Search PubMed⌕ Search

Biomedical subjects

A Ammar

Publications and source records attributed to A Ammar.

At least 73 records · Page 4Linked to original sources
PubMed1993

Reversibility of severe brain stem dysfunction in children.

The very popular concept of brain death can lead to a defeatist attitude when confronted by a patient with severe brain stem dysfunction. This problem is compounded by the constant controversy surrounding the establishing of criteria to determine brain death. Many young doctors tend to accept the precondition of irreversibility as being any condition that is not explicitly listed in the examples of potentially reversible conditions. In children, however, with compressive brain stem dysfunction, decompressive surgery can lead to a reversal of the dysfunction. In the last three years, we have had the opportunity to observe 5 children who were deeply comatose and apnoeic. All were suffering from compression of the brain stem and experienced dramatic return of brain stem function following emergency decompression. The implications of these findings on the therapeutic attitude towards compressive brain stem lesions in children are exposed. In children with severe brain stem dysfunction, and no evidence of brain stem destruction, decompressive surgery should be undertaken before a diagnosis of brain death is considered.

Brain Abscess↗
PubMed1993

Doppler-derived aortic valve gradients: imaging versus non-imaging techniques.

BACKGROUND: Quantitative Doppler echocardiography has become an established method for estimating aortic valve area in aortic stenosis, replacing cardiac catheterization as the confirmatory study. The technique is time consuming, especially when measuring the transaortic velocity, which is performed by convention. This is accomplished by interrogating multiple windows with a non-imaging probe to record the maximal velocity. To determine how the examination could be expedited, we prospectively compared aortic valve gradients measured by Pedof and duplex transducers. METHODS: One hundred eighty-two consecutive patients with native aortic valve disease, mechanical or bioprosthetic aortic valves were studied. Two technicians measured maximal transaortic valve velocities from apical, subcostal, right parasternal and suprasternal notch windows with a 2 MHz Pedof probe and from the apical window with a 3-3.5 MHz duplex probe using color flow to orient the continuous wave beam. Angle-corrected and non-angle-corrected signals were recorded. There were 109 comparisons read by two observers; intra- and inter-reader variations were 0.4% and 2.0%, respectively. RESULTS: Duplex imaging velocity gradients were consistently smaller than Pedof non-imaging measurements with a mean +/- 1 standard deviation difference between peak velocities of 0.40 +/- 0.71 meters per second (m/s) for angle-corrected, and 0.76 +/- 0.68 for non-angle-corrected signals (both p < 0.001). Technician variability accounted for some of the difference (p < 0.02). CONCLUSION: Although non-imaging and imaging methods share the apical window, the Pedof probe scans unlimited planes to locate the maximal aortic valve gradient, whereas the duplex probe is confined to the plane providing the optimal two-dimensional image. Therefore, Doppler echocardiographic estimations of aortic valve areas still require careful, time-intensive non-imaging recordings of transaortic velocities.

Aortic Valve↗
PubMed1992

Purification and identification of a CD25 expression inhibitory protein from cell-free supernatants of chronically HIV-infected promonocytic cells.

The CD25 (IL-2-R alpha) cell surface glycoprotein expressed transiently during T-cell activation is implicated in the high affinity IL-2 receptor. This paper shows that cell-free supernatants from chronically HIV-infected promonocytic cells spontaneously produce a soluble factor which inhibits CD25 expression on PHA-activated human PBMC. We purified the CD25 expression inhibitory activity by a factor 12,350, using XM50 ultrafiltration, Superose 12 molecular sieving chromatography and MonoQ anion-exchange chromatography. Then we associated this activity to one single spot (M(r) 29,000, pI 6.8) on an O'Farrell two-dimensional gel. Our data demonstrate that this protein (M(r) 29,000, pI 6.8) is released from HIV-infected promonocytic cells and suggest that this factor is a new monokine regulating the T-cell activation process.

Cell Line↗
PubMed1992

Pattern of subarachnoid haemorrhage in Saudi Arabia.

It has often been claimed that subarachnoid haemorrhage (SAH) is a rare condition in the Middle East. A 7-1/2-year retrospective study was undertaken to substantiate or disprove this claim. It was found that although the condition is less common than the global average, it was not as rare as previously supposed. The pattern of distribution throughout the population, in terms of sex, was significantly different. The possible reasons for this are discussed.

Adolescent↗
PubMed1992

Repair of skull base dural defects: the dura sandwich. Technical note.

A technique for skull base dural defect repair is presented, using two layers of periosteum and biological (Tisseel glue), one on either side of the defect. The method is reliable and relatively simple, and was used to repair a recurrent skull base encephalocoele with great success. The method has application in the reconstruction of any dural defect, whether congenital, traumatic or surgical.

Dura Mater↗
PubMed1992

Abnormal expression of IL-2R beta (p70)-binding polypeptide on HIV-infected patients' cells.

The constitutively expressed IL-2R beta (p70) chain participates in the formation of high-affinity (h.a.) IL-2R and transduces IL-2-mediated signals to normal cells. Its expression on HIV-infected patients' PBMC was evaluated and was found to be decreased in both nonstimulated CD4+ and CD8+ cells. Mitogenic cell stimulation induced IL-2R beta chain expression on both CD4+ and CD8+ cells from asymptomatic and persistent generalized lymphadenopathy patients but not on those from AIDS patients. Comparison of mean fluorescence intensity of IL-2R beta positively stained cells from normals and patients did not reveal significant differences. Cross-linking of 125I-rIL-2 on patients' PHA-blasts revealed decreased signals corresponding to both IL-2-binding chains and, in some cases, neither IL-2R alpha nor IL-2R beta chains could be detected. Decreased expression of IL-2R beta polypeptide was associated with impaired accumulation of the corresponding mRNA transcripts. Binding experiments with 125I-rIL-2 under h.a. conditions showed a decreased number of IL-2-binding sites/cell which was more pronounced in patients with AIDS than in patients with less advanced clinical stages. In vitro HIV infection of normal PHA-blasts also resulted in a decreased number of h.a. IL-2R/cell. High concentrations of rIL-2 in the absence of other mitogenic stimuli induced a decreased cell proliferation and expression of the IL-2R alpha chain and did not enhance the constitutive NK and the generation of LAK activity in several patients, suggesting an impaired IL-2R beta chain-mediated cell activation.

Antibodies, Monoclonal↗
PubMed1992

Postnatal ontogenesis of vasopressin receptors in the rat collecting duct.

The ontogenesis of vasopressin receptors in the rat collecting duct was studied by measuring the binding of [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid),2-O-methyltyrosine,4-threonine,8-ornithine,9-125I-tyrosylamide+ ++]-vasotocin (125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH(9)2]-OVT) to isolated cortical collecting ducts (CCD), outer medullary collecting ducts (OMCD) and inner medullary collecting ducts (IMCD) microdissected from collagenase-treated kidneys of 2- to 34-day-old rats and adult animals. The stereospecificity for recognition of a series of seven vasopressin structural analogues by CCD and OMCD receptors reveals that the labeled binding sites identified in 11- to 16-day-old and adult rats are homologous respectively and contain a major population of V2 type and a minor population of V1a type of vasopressin receptors. At all postnatal stages examined, the receptor density (expressed as 10(-18) mol radioligand bound per square millimeter tubular outer surface area) decreases gradually from the CCD to the IMCD. For the three segments, the numbers of receptors detected remained constant during the first 2 weeks after birth and increased sharply after 20 days to reach the corresponding adult levels during the fifth week.

Animals↗
PubMed1992

Pharmacological characterization of V1a vasopressin receptors in the rat cortical collecting duct.

Vasopressin receptors in distal segments of the rat nephron were identified in isolated tubules using two labeled ligands: the [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine,4-threonine,8-ornithine,9-125I-tyrosylamide]- vasotocin [125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT] and the linear analogue, Phaa1,D-Tyr(Me)2,Phe3,Gln4,Asn5,Arg6, Pro7,Arg8,125I-Tyr-NH2(9) [125I-Tyr-NH2(9)-linear antagonist (LA)-V1a)]. Specific 125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]-OVT binding to cortical collecting ducts (CCD) was saturable with incubation time and dose, reversible after elimination of free ligand, and characterized by the following rank order for recognition of vasopressin analogues: desGly9-d-(CH2)5-[Tyr(Et)2,Val4]arginine vasopressin (AVP) greater than or equal to d(CH2)5[Tyr-(ET)2,Val4]AVP greater than or equal to AVP greater than or equal to d(CH2)5[Tyr(Me)2]AVP = 1-desamino-8-D-arginine vasopressin (DDAVP) greater than or equal to Tyr-NH2(9)-LA-V1a greater than [8-arginine]vasotocin (AVT) greater than d(CH2)5[Tyr(Me)2, Thr4,Tyr-NH2(9)]OVT greater than oxytocin (OT) greater than [Phe2,Orn8]VT much greater than [Thr4,Gly7]-OT. Scatchard plots of dose-dependent 125I-Tyr-NH2(9)-LA-V1a binding to medullary thick ascending limbs (MTAL), CCD, and outer medullary collecting ducts (OMCD) revealed the presence of high- and low-affinity binding sites corresponding to V1a and V2 vasopressin receptors, respectively; the densities of V1a receptors are approximately 20% of the total number of vasopressin receptors in CCD and 5% in MTAL and OMCD.

Animals↗
PubMed1992

Human immunodeficiency virus-infected adherent cell-derived inhibitory factor (p29) inhibits normal T cell proliferation through decreased expression of high affinity interleukin-2 receptors and production of interleukin-2.

Adherent cells from HIV-infected subjects as well as in vitro HIV-infected normal adherent cells produce spontaneously a 29-kD (p29) factor that inhibits mitogen-induced proliferation of normal T cells. p29 mediates a partial dose-dependent inhibition of total protein synthesis in both nonstimulated and PHA-activated cells that is associated with impaired PHA-induced expression of IL-2 receptor (IL-2R)alpha chain, HLA-class II molecules, and production of IL-2 by these cells; conversely, p29 does not modify the expression of IL-2R beta chain, 4F2, CD9, or transferrin receptor, or the production of IL-1 and TNF alpha by the cells. 1 h preincubation of the cells with p29 is sufficient to detect its biologic activity and added rIL-2 abrogates p29-induced inhibition of IL-2R alpha chain expression; however, p29 does not display any biologic effect on already expressed IL-2R alpha chains. The impaired expression of IL-2R alpha chain mediated by p29 is not due to a decreased accumulation of the corresponding mRNA transcripts, but is associated with a two-fold increase of intracellular cAMP. Binding experiments with 125I-rIL-2 reveals that p29 induces a 50% decrease in the number of both high and low affinity IL-2R per cell. p29 also inhibits alloantigen-induced proliferation of PBMC, whereas it does not modify IL-2-dependent proliferation of 48-h PHA-blasts that already express high affinity IL-2R. These findings indicate that p29 mediates its biologic activity during early stages of T cell activation affecting the expression of high affinity IL-2R and production of IL-2, through a nontranscriptional mechanism involving an increase of intracellular cAMP.

Cyclic AMP↗
PubMed1992

[Endobronchial neurogenic tumors].

Endobronchial neurogenic tumours are exceptional and little known. The authors report two cases of such tumours: a neurofibroma of the right main bronchus in a 32 year old man and a schwannoma of the left main bronchus in a 10 year old child. Pneumonectomy was necessary in both cases due to destruction of the pulmonary parenchyma distal to the obstruction. The incidence of this type of tumour is estimated to be between 0.2 and 4%. They may be either schwannomas or neurofibromas, the discovery of which always raises the problem of the possible association of von Recklinghausen's disease malignant forms, neurogenic sarcomas or malignant schwannomas may also be encountered. The diagnosis is based on endoscopy which reveals the tumour and allows biopsy. Treatment of these essentially benign tumours should be conservative, provided the diagnosis is made early, prior to parenchymal destruction. The prognosis is poor in the malignant forms and chemotherapy may be useful in malignant schwannomas.

Adult↗
PubMed1992

Interleukin 2 production and interleukin 2 receptor expression by human immature leukemic T cells.

In order to determine the role of interleukin 2 (IL2) on the proliferation of leukemic cells from patients with T-cell acute lymphoblastic leukemia (T-ALL) we studied the production of IL2, the function of IL2 receptors (IL2R) expressed on T-ALL cells and their IL-2-dependent in vitro proliferation. Leukemic cells from six out of 17 T-ALL/T-cell non-Hodgkin's lymphoma patients with a prothymocyte (stage I) or a mature thymocyte (stage III), but not with a common thymocyte (stage II) phenotype, could proliferate, in a dose-dependent manner, in response to recombinant IL2 (rIL2) and anti-Tac and TU27 moAbs as well as polyclonal anti-IL2 purified immunoglobulin G could inhibit this IL2-induced cell proliferation. Both crude or/and Amicon-concentrated media conditioned by T-ALL cells from 10 out of 13 tested patients contained IL2 activity as assessed by colorimetric biological and immunoenzymatic assays; this biologic activity was due to a 14.5 kDa molecule adsorbed by anti-IL2 antibodies in an immunoaffinity assay. Although less than 10% of fresh leukemic cells expressed IL2R alpha (Tac) chain, a 24 h cell incubation in the absence of any mitogenic stimulation induced IL2R alpha chain expression in five out of 13 patients (11-83% Tac+ cells). Morever, Tac mRNA transcripts could be detected in fresh cells from all 10 patients tested. Staining of fresh leukemic cells with an IL-2R beta-chain-specific monoclonal antibody and flow cytometry analysis revealed that 4-13% of leukemic cells were positive. Binding experiments with 125I-rIL2 showed a small number of high affinity IL2R on fresh cells from three T-ALL patients (114-200 sites/cell, dissociation constant = 101-181 pm). Finally, antibodies against IL2R alpha, IL2R beta and IL2 could inhibit both IL2 driven and spontaneous cell proliferation of most patients' T-ALL cells, although in some cases an heterogenous pattern of inhibition was observed. Taken together, these findings strongly suggest that an IL2/IL2R-dependent mechanism could be involved in the proliferation of some T-ALL cells.

Antigens, CD↗
PubMed1991

CSF hydrocele--unusual complication of V-P shunt.

CSF hydrocele as a complication of migration or extrusion of the peritoneal end of the V-P shunt has rarely been reported. Here the case of a 6 month old infant, born at 28 weeks gestational age, is reported. The baby was noted to have scrotal swelling, exacerbated by crying, two months after insertion of ventriculoperitoneal shunt. The hydrocele resolved following revision of the shunt. Possible pathophysiological causes are discussed.

Cerebrospinal Fluid Shunts↗
PubMed1991

Receptors for neurohypophyseal hormones along the rat nephron: 125I-labelled d(CH2)5[Tyr(Me)2, Thr4, Orn8, Tyr-NH(2)9] vasotocin binding in microdissected tubules.

A microassay was developed to measure the binding of the labelled monoiodinated analogue [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-O-methyltyrosine, 4-threonine, 8-ornithine, 9-125I-tyrosylamide]vasotocin [125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT] to isolated nephron segments microdissected from collagenase-treated rat kidneys. When determined using 1.7 nM labelled ligand at 4 degrees C, specific binding sites (expressed at 10(-18) mol 125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT bound/mm tubule length) were found in medullary thick ascending limbs (MTAL), 1.67 +/- 0.49; cortical thick ascending limbs, 2.20 +/- 0.80; cortical collecting ducts, 2.39 +/- 0.86; outer medullary collecting ducts (OMCD), 2.54 +/- 0.53 and inner medullary collecting ducts, 5.33 +/- 0.40, whereas no specific binding could be detected in glomeruli and proximal tubules. Specific 125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT binding to OMCD was saturable with incubation time and reversible after elimination of free labelled ligand (the association and dissociation rate constants at 4 degrees C were 1.06 x 10(7) M-1 min-1 and 1.95 x 10(-2) min-1 respectively). The stereospecificity of MTAL and OMCD binding sites was assessed in competitive experiments revealing the following recognition pattern for a series of eight vasopressin analogues:dDAVP greater than AVP greater than d(CH2)5-[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT = AVT = OT greater than d(CH2)5[Tyr(Me)2]AVP = [Thr4, Gly7]OT greater than [Phe2, Orn8]VT, whereas pharmacological concentrations of insulin and glucagon did not impair radioligand binding. These results indicate that the detected labelled binding sites might correspond mainly to physiological V2 vasopressin receptors.

Animals↗
PubMed1991

A comparison of single prostaglandin E2 vaginal tablet with prostaglandin E2 vaginal pessaries for induction of labor at term.

This study represents the first of its kind in Kuwait. Two preparations of prostaglandin E2 (PGE2) have been compared as agents for induction of labor. In a randomized controlled study of 200 women of low parity and unfavorable cervical induction features induction of labor by means of a single vaginal tablets of PGE2 was compared with locally prepared PGE2 vaginal pessaries. The gradual increase of uterine contractions and the establishment of labor in a similar way to that observed during spontaneous labor was more apparent after PGE2 tablets. Labor induction was successful in 80% of patients in PGE2 tablet group compared with 59% in PGE2 pessaries group. The incidence of cesarean section was equal in both groups (4%), but none was performed due to uterine hyperactivity. The data presented indicate that the PGE2 vaginal tablet is safe and effective in induction of labor in healthy women at term.

Administration, Intravaginal↗
PubMed1991

Differentiating medulloblastoma in adults.

We present two cases of medulloblastoma in adults patients showing extensive astrocytic differentiation. In one case, there was synchronous oligodendroglial differentiation, both changes appearing after treatment with radiotherapy. The possible role of radiotherapy in the differentiation is discussed.

Adult↗