Neurosurgical anatomy of the anterior interhemispheric approach for aneurysms of the anterior communicating artery (26.6.92)

Summary The anterior interhemispheric approach for aneurysms of the anterior communicating artery was studied in ten cadavers. This approach presents several advantages over the pterional approach widely used in neurosurgery. It allows direct access to the region of the anterior communicating artery complex with minimal retraction of the brain and preservatioin of the olfactory tract and the gyrus rectus.

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Bases anatomiques de l'abord inter-hémisphérique antérieur lors de la chirurgie des anévrysmes de l'artère communicante antérieure

Résumé Ce travail concerne l'abord neurochirurgical des anévrysmes de l'artére communicante antérieure par voie frontale interhémisphérique. L'étude anatomique a été réalisée sur dix sujets. Cette exposition possède de nombreux avantages comparée à la voie ptérionale habituelle : voie d'abord reduite médiane permettant une visualisation directe et symétrique du complexe artériel de l'artére communicante antérieure ; avec le moindre manipulation et retraction du cerveau en respectant les voies olfactives et le gyrus rectus.

     

Follicular thyroid lesions coexisting with Hashimoto's thyroiditis: incidence and possible sources of diagnostic errors

Our objectives were to study the types and incidence of thyroid follicular lesions coexisting with Hashimoto's thyroiditis (HT), the pitfalls in their cytodiagnosis, and the effect on management. All cases of HT diagnosed by fine-needle aspiration (FNA) and/or histology over a 7-yr period were retrospectively studied. HT coexisted with follicular adenoma (FA) in 6 cases, follicular variant of papillary carcinoma (FVPC) in 1 case, and goitrous nodule (GN) in 2 cases. The overall incidence rates of thyroid neoplasm and goitrous nodules coexistent with HT were 15% and 3.5%, respectively. A preoperative FNA diagnosis was available in 10 histologically proven cases of HT. A false-positive diagnosis of follicular neoplasm (FN) that led to unnecessary thyroidectomies was given in 3 cases. In 2 of these, the cytological diagnosis was HT with the possibility of coexisting FN, and in the third case, the cytological finding of HT was misinterpreted as FN. The main causes of these diagnostic pitfalls were the presence of hyperplastic follicular cells with nuclear pleomorphism, a paucity of lymphoid cells in burned-out HT, and lack of ones exposure. Nuclear pleomorphism was observed in none of the follicular adenomas. FNA diagnosed accurately the coexisting lesions in 6 cases; 3 FA, 1 FVPC, and 2 GN, but it did not sample HT. In one case, FNA diagnosed correctly both HT and the coexisting FA. Therefore, the presence of a coexistent neoplasm or goitrous nodule reduced the chances of sampling HT by 85.7%, with no false-negative results. Indeed, aspiration on and around the thyroid nodule helps in sampling HT. However, HT may dominate the smear and obscure neoplasia. This can be avoided if the procedure is performed by the pathologist and the aspiration is done on the nodule only. The overlapping cytological features of FN and HT were the main causes of false-positive results. This can be reduced by avoiding the diagnosis of FN in the presence of follicular-cell pleomorphism and/or moderate to excessive numbers of lymphoid cells, provided proper aspiration technique is maintained.     

A novel HLA-B*39 allele (HLA-B*3916) due to a rare mutation causing cryptic splice site activation

A novel HLA-B*39 variant, found in an African patient with sickle cell anemia undergoing bone marrow transplantation is described. Initially suspected by inconsistent serological typing (B-blank, Bw6), then recognized by PCR-SSP, and finally characterized by nucleotide sequencing, this novel allele is designated HLA-B*3916. It differs from HLA-B*3910 by a point mutation (G to C) at position 17 of exon 3 causing glutamine to histidine change at codon 96 of alpha(2) domain, a conserved position among HLA class I alleles. cDNA sequence analysis further revealed the presence of both normally and abnormally spliced mRNA species in established cell lines. The abnormal species correspond to partial truncation of exon 3 presumably due to the nucleotide change in exon 3, which constitutes a new consensus acceptor splice site within this exon. We postulate that the observed blank is essentially the consequence of qualitative change in a critical region of this novel antigen as abnormal mRNA species are relatively less abundant than normal species. Because the residue 96 of the HLA class I heavy chain is directly involved in interaction with alpha(2)m, another interesting possibility is that an aminoacid change in this position would perturb such interaction and consequently could affect the serological specificity of B*3916, or its expression or both.     

Pneumocystis carinii f. sp. hominis is not infectious for SCID mice

The infectious power of Pneumocystis carinii f. sp. hominis was explored by inoculating SCID mice intranasally with either P. carinii f. sp. hominis or P. carinii f. sp. muris isolates. Only mice inoculated with mouse parasites developed Pneumocystis pneumonia, as assessed by microscopy and PCR. These results suggest that humans do not contract pneumocystosis from animals.     

T lymphocytemediated cytotoxicity in hbsag-positive liver disease

It has been suggested that cellular immune responses to the hepatitis B virus are of importance in the production of liver cell damage in both acute and chronic hepatitis. An assay has now been developed which detects lymphocytes cytotoxic for target cells coated with the hepatitis B surface antigen (HBsAg). The reaction could be blocked by prolonged pre-incubation of lymphocytes with highly purified HBsAg and studies with lymphocyte subpopulations have shown that T lymphocytes were the principle effector cells.

When lymphocytes from twenty-three patients with acute hepatitis were used, cytotoxic T cells were demonstrable during the recovery phase, but not in the first 3 weeks of the illness. However, when these same lymphocytes were extensively washed, cytotoxicity was then detected in all the patients, even at the time of presentation. In patients with HBsAg-positive chronic liver disease the results with the standard assay were largely within the normal range, but again with extensive lymphocyte washing cytotoxicity was detected in all of the patients with untreated chronic active hepatitis and in five out of six with more minor histological lesions. The results in five carriers with normal liver histology were completely different, cytotoxicity remaining undetectable even after the extensive washing procedure.

The results suggest that blocking factors, possibly antigen or antigen–antibody complexes, could be interfering with the detection of sensitized T cells in patients with acute and chronic hepatitis, but that there is a true absence of sensitization to HBsAg in healthy carriers with normal liver histology.

     

Copolymer-monomer miscibility during copolymerization

Significant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N-vinyl-2-pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.-% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (T_g) behaviour of the products of the γ-ray initiated copolymerization at various fractional conversions (C) and 2 the T_g behaviour of low-conversion samples of poly(VP-co-BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co-existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]_Θ measured. The chain expansion factors thereby derived from [η] and [η]_Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization.     

Mitochondrial DNA Heterogeneity in Tunisian Berbers

Berbers live in groups scattered across North Africa whose origins and genetic relationships with their neighbours are not well established. The first hypervariable segment of the mitochondrial DNA (mtDNA) control region was sequenced in a total of 155 individuals from three Tunisian Berber groups and compared to other North Africans. The mtDNA lineages found belong to a common set of mtDNA haplogroups already described in North Africa. Besides the autochthonous North African U6 haplogroup, a group of L3 lineages characterized by the transition at position 16041 seems to be restricted to North Africans, suggesting that an expansion of this group of lineages took place around 10500 years ago in North Africa, and spread to neighbouring populations. Principal components and the coordinate analyses show that some Berber groups (the Tuareg, the Mozabite, and the Chenini‐Douiret) are outliers within the North African genetic landscape. This outlier position is consistent with an isolation process followed by genetic drift in haplotype frequencies, and with the high heterogeneity displayed by Berbers compared to Arab samples as shown in the AMOVA. Despite this Berber heterogeneity, no significant differences were found between Berber and Arab samples, suggesting that the Arabization was mainly a cultural process rather than a demographic replacement.     

Changes in the level of antioxidants in the blood from mice infected with<Emphasis Type="Italic"> Trichinella spiralis</Emphasis>

The biological reaction caused by oxygen-derived free radicals at the molecular and cellular levels involves many different biochemical components which can be directly damaged by oxidizing radicals. As such a reaction may lead to pathological processes, defence mechanisms have evolved to limit the rate of free radical production. These mechanisms employ low-molecular-weight non-enzymatic antioxidants and antioxidant enzymes which are inducible by oxidant stress. In this study, the activity of two antioxidant enzymes, superoxide dismutase (EC 1.15.1.1) and glutathione peroxidase (EC 1.11.1.9), and the level of non-enzymatic antioxidants (total antioxidant status) in the blood from mice infected with Trichinella spiralis was examined. We observed a statistically significant, up to above twofold increase (relative to the control value in uninfected mice) in the level of both enzymes as well as in the total antioxidant status. An intensification of antioxidant processes during trichinellosis could be related to the presence of T. spiralis larvae, which may induce phagocytes to generate free radicals. Our research shows that the maximum growth in antioxidant activity in the blood appears during the period of the greatest muscle damage caused by T. spiralis infection at 3–7 weeks post-infection.     

Schistosomiasis of the spinal cord in a Yemeni boy. A report of a case with brief review of literature

A 13-year old Yemeni boy who presented with flaccid paraplegia was thought to have a spinal cord tumor on myelography. Microscopic examination of surgically excised material revealed bilharzial granulomas. Brief review of relevant literature on schistosomiasis of the spinal cord, with particular reference to the Middle East, is presented.