Biomedical subjects
Publications and source records attributed to D Rout.
Two cases of intracranial cystic meningiomas are reported. Neuroradiological and intraoperative diagnoses in both cases were cystic astrocytoma. However routine biopsy during the intra-operative period and an accurate interpretation during frozen-section will establish the diagnosis of cystic meningioma. Complete excision of cyst wall of the meningioma during the surgery will minimise the incidence of recurrence of these benign tumours.
The ends (telomeres) of eukaryotic chromosomes must have special features to ensure their stability and complete replication. Studies in yeast, protozoa, slime moulds and flagellates show that telomeres are tandem repeats of simple sequences that have a G-rich and a C-rich strand. Mammalian telomeres have yet to be isolated and characterized, although a DNA fragment within 20 kilobases of the telomeres of the short arms of the human sex chromosomes has been isolated. Recently we showed that a chromosome from the fission yeast Schizosaccharomyces pombe could, in some cases, replicate as an autonomous mini-chromosome in mouse cells. By extrapolation from other systems, we reasoned that mouse telomeres could be added to the S. pombe chromosome ends in the mouse cells. On setting out to test this hypothesis we found to our surprise that the telomeric probe used (containing both the S. pombe and Tetrahymena thermophila repeats) hybridized to a series of discrete fragments in normal mouse DNA and DNA from a wide range of eukaryotes. We show here that the sequences hybridizing to this probe are located at the telomeres of most, if not all, human chromosomes and are similar to the Tetrahymena telomeric-repeat component of the probe.
Collagenase and stromelysin are two metalloproteinases produced mainly by connective tissue cells and involved in the breakdown of the extracellular matrix. cDNA clones for both of these genes have been isolated and sequencing has shown them to be closely related. The collagenase and stromeylsin cDNA clones have been used to assign these genes to the long arm of chromosome 11 in the regions 11q21-22.1 and 11q22.2-22.3, respectively. This has been achieved using somatic cell hybrids and in situ hybridization. In addition a Taq1 restriction fragment length polymorphism has been demonstrated using the stromelysin cDNA.
Cytochromes P-450 represent a superfamily of enzymes with a central role in the metabolism of drugs, chemical toxins, and carcinogens. We have used genetic analysis to establish the complexity and catalytic function of a recently identified constitutively expressed murine hepatic cytochrome P-450 encoded by P450-2C. Southern blotting analysis shows that there are at least seven or eight genes within this family in the mouse and rat and that DNA restriction fragment length variants between different mouse inbred strains are observed. Analysis of recombinant inbred strains derived from these parent strains shows (i) these genes are clustered within 1 centimorgan, (ii) this gene family does not correspond to any of the known cytochrome P-450 loci or map near any well-characterized genomic markers, and (iii) this gene family segregates to within 1-2 centimorgans of a locus controlling constitutive aryl hydrocarbon hydroxylase activity in mice. With use of Chinese hamster/mouse somatic cell hybrids, the P450-2C locus was assigned to a region of mouse chromosome 19 that appears to be syntenic with the previously mapped human P450C2C locus on human chromosome 10. By in situ hybridization to mitotic mouse chromosomes, we have localized this region to the tip of chromosome 19. These results are discussed in relation to the physiological roles of this P-450 family in foreign compound metabolism and steroid oxidations.
The cytochrome P-450 monooxygenase system possesses catalytic activity toward many exogenous compounds (e.g., drugs, insecticides, and polycyclic aromatic hydrocarbons) and endogenous compounds (e.g., steroids, fatty acids, and prostaglandins). Multiple forms of cytochrome P-450 with different substrate specificities have been isolated. In the present paper we report the isolation and sequence of a cDNA clone for the human hepatic cytochrome P-450 responsible for mephenytoin (an anticonvulsant) oxidation. The mephenytoin cytochrome P-450 is analogous to the rat cytochrome P-450 form termed PB-1 (family P450C2C). We also report that human PB-1 is encoded by one of a small family of related genes all of which map to human chromosome 10q24.1-10q24.3. The endogenous role of this enzyme appears to be in steroid oxidations. This cytochrome P-450 family does not correspond to any of the hepatic cytochrome P-450 gene families previously mapped in humans.
A cloned 2184-bp cDNA coding for human interstitial retinol-binding protein (IRBP) has been isolated and sequenced. The probe hybridized to a 5.2-kb poly(A) RNA from human retinas. Nineteen tryptic peptides (363 amino acids) sequenced and purified from bovine IRBP could be aligned with 86-88% homology to the translated sequence. Two segments approximately 200 amino acids long were found to have a 41% residue identity, suggesting an internal duplication event. This cloned cDNA was used to probe DNA samples from a panel of 29 rodent-human somatic cell hybrids, mapping the structural gene for IRBP to chromosome 10. In situ hybridization suggested a regional localization near the centromere (p11.2----q11.2), although a secondary site of hybridization at q24----25 was also observed.
We show that chromosome-mediated gene transfer can provide an enriched source of DNA markers for predetermined, subchromosomal regions of the human genome. Forty-four human DNA recombinants isolated from a HRAS1-selected chromosome-mediated gene transformant map exclusively to chromosome 11, with several sublocalizing to the Wilms tumor region at 11p13. We present a detailed molecular map of the deletion chromosomes 11 from five WAGR (Wilms tumor/aniridia/genitourinary abnormalities/mental retardation) syndrome patients, three of which are at the limits of cytogenetic resolution but shown here to be molecularly distinguishable and overlapping. We can define ten distinct regions of the short arm of chromosome 11, five of which subdivide band 11p13. We also map two independent 11p13 translocation breakpoints to within the smallest region of overlap defined by the WAGR deletions. The first comes from a patient with familial aniridia, and the second from a patient with Potter facies and genitourinary dysplasia. The close similarities in map location and affected cell lineage for Wilms tumor and genitourinary dysplasia suggest that they may be alternative manifestations of mutation at the same locus.
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The human ERBA2 gene has been mapped to chromosome 17q21.3 by in situ hybridization. A second hybridization site at 17q25 was greatly reduced by high stringency washes, indicating the presence of an additional member of the ERBA2 family at this location. Southern blot hybridization using identical conditions did not reveal additional bands, and hybridizations done at sufficiently low stringency to reveal further bands produced multiple bands rather than the single additional band expected from the in situ results. Direct comparisons of in situ and Southern hybridizations should therefore be treated with caution. The location of these two oncogenes may be significant in cases of acute promyelocytic leukaemia and acute nonlymphocytic leukaemia.
The oestrogen receptor gene (ER) was mapped by in situ hybridization. Using a human cDNA probe containing the coding sequence for the oestrogen receptor, the gene was localized to 6q24----q27.
Experience with direct exploration of the pineal region in 22 consecutive patients is reported. Of these cases, mass lesions with obstructive hydrocephalus were found in 19; the remaining 3 had arteriovenous malformations of the pineal region. Of the 19 mass lesions, 5 (26%) were benign and curable. Although a preliminary shunt was routinely provided in all patients with obstructive hydrocephalus before exploration of the pineal region, the condition of five (26%) worsened after the shunt operation, requiring emergency decompression of the pineal tumor. A transtentorial approach through a right occipital craniotomy was uniformly employed in all cases. Overall mortality was less than 5%. These observations and results support the policy of direct exploration of all lesions in the pineal region.
Six cases of bacterial intracavernous carotid artery aneurysms of extravascular origin secondary to cavernous sinus thrombophlebitis are reported along with a review of 12 similar cases collected from the literature. Of the authors' six cases, there were three children and three adults. Meningitis was found in five patients. All patients received prolonged antibiotic therapy. Spontaneous resolution of the aneurysm occurred in one patient, thrombosis of the internal carotid artery in another, and progressive enlargement of the aneurysm was seen on sequential angiography in the other two. Evidence of associated arteritis was present in all of the patients. Carotid ligation for persistent ophthalmoplegia was carried out in two patients, of whom one had a giant aneurysm and the other progressive aneurysm enlargement. The results of treatment were good in all cases. The authors believe that carotid arteriography is obligatory in cases of cavernous sinus thrombophlebitis in which ophthalmoplegia persists despite adequate antibiotic therapy.
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Two unusual cases of symptomatic Rathke's cleft cysts are reported. In one, the cyst was entirely suprasellar with a normal sella turcica. The gross visual failure, hypothalamic disturbances, and hypopituitarism of the patient resolved after a transfrontal aspiration and partial excision of the wall of the cyst. The second patient was a pituitary dwarf with hypothalamic dysfunction, but with normal vision. The patient had a large intrasellar cyst that exhibited marked suprasellar extension with calcification of the capsular rim. After transsphenoidal aspiration and partial excision of the wall of the cyst, the patient achieved a satisfactory recovery. The differential features between Rathke's cleft cyst and craniopharyngioma are highlighted.
A case of cervical intramedullary schwannoma without evidence of von Recklinghausen's disease is reported. The hypotheses regarding its histogenesis and the difficulty in diagnosis on the frozen section obtained at biopsy are discussed, along with a review of literature covering 15 previously reported cases.
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The successful retrieval of a catheter fragment from the abdominal aorta by the wire snare technique, thus avoiding a major laparotomy, is reported. Whereas there are many published reports on the use of this technique in the venous circulation, similar experiences in the arterial circulation have been reported but rarely.
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