Biomedical subjects
Publications and source records attributed to M C Lim.
Cushing's disease in pregnancy is rare and is associated with an increased incidence of maternal morbidity, premature delivery, spontaneous abortions and stillbirths. We report a successful term pregnancy in a patient with Cushing's disease due to a pituitary microadenoma. The literature is reviewed.
Adrenal cortical carcinoma is a rare tumour with a poor prognosis. We report a patient with metastatic adrenal cortical carcinoma who responded dramatically to Mitotane (o,p'-DDD). Unlike previous reports of metastatic adrenal cortical carcinoma in which complete remission was obtained with high dose Mitotane treatment, the dose of Mitotane used in this patient was low. However, she developed unusual side-effects such as hyperpigmentation, low plasma cortisol and high adrenocorticotropic (ACTH) levels. The side effects closely resemble those in Nelson's syndrome and were reversed by cortisone replacement. The mechanism of actions of Mitotane is discussed with emphasis on its effect on corticosteroid metabolism.
We describe a Chinese family with three siblings, all females, presenting with the Wolfram Syndrome. All three cases had almost similar clinical presentation of insulin-dependent diabetes mellitus, with rapid development of severe renal and retinal complications. Two siblings died at age thirty and thirty-one years of end-stage renal failure. All three cases had visual symptoms since early childhood progressing rapidly to loss of vision. Two of the three siblings had severe diabetic retinopathy requiring laser photocoagulation. These presentations are in contrast to most reported cases of the Wolfram syndrome where advanced diabetic eye complication is a rare feature. We also present several features present in one of the siblings, viz., microcephaly, microstomia, clinodactylyl, brachydactylyl, empty sella syndrome and severe hypoplasia of the right internal carotid vessels associated with mild narrowing of the left internal carotid artery which have not been previously described.
Relapsing polychondritis is a rare multisystemic connective tissue disorder found mainly in Caucasians. Oriental patients with relapsing polychondritis are uncommon. We report 2 Chinese patients with relapsing polychondritis who had severe laryngotracheal narrowing requiring tracheostomy. Unlike most patients, there was marked costal chondritis resulting in depression of the anterior chest wall with minimal involvement of other joints. One of the patients had treatment with prednisolone, dapsone, azathioprine, cyclophosphamide and cyclosporin A at various stages of the disease without significant remission of the disease.
The Lifschytz-Lindley model of spermatogenesis in heterogametic animals postulates a stage of gene inactivation during spermatogenesis, which affects the X-chromosome and the autosomes at different times. The frequent male infertility of X-ray induced X-autosome translocations is attributed to disruption in the timing of this stage by breaks that occur in the interior euchromatic portion of the X. Indeed, all male-fertile X-ray induced translocations between the X and an autosome had their breakpoints in the proximal or distal portion of the X. We now show that this was true also for 16 male-fertile X-autosome translocations that had been induced by an alkylating agent, diepoxybutane (DEB). The significantly higher proportion of male-fertile X-translocations in this experiment than in experiments with ionizing radiation apparently is due to a preference of diepoxybutane for the induction of breaks in the "permissive" regions of the X. Older data suggest that this preference is even stronger for mustard gas as chromosome-breaking agent. While these data do not add further evidence to the Lifschytz-Lindley model, they remove a potential objection to it.
Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains. The sex-chromosome constitution of a cell could be judged objectively if X and Y chromosomes and ploidy were all scored. A bias arose if only Y chromosomes and ploidy were scored but could be corrected statistically. There was no sign of other forms of bias. The original contiguity of X and Y second metaphases in vivo was very occasionally evident in the preparations. Most of the subhaploid aneuploid counts were assumed to be artifactual. The incidence of truly aneuploid second metaphases in 13 strains was estimated as 0.38+/-0.12%. The estimated average rate per chromosome was 0.019+/-0.006%, with a comparable order of magnitude for the sex chromosomes alone. Simultaneous aneuploidy of two or more chromosomes of the haploid set was estimated to be very rare. Of the spreads from 13 strains, 9.6% were polyploid (2N, 3N, 4N) and showed most of the possible combinations of sex chromosomes. Nearly all the polyploid spreads were considered to arise by artifactual cell fusion at the time of second metaphase during the preparative technique, especially of the X and Y daughter-cell products of the first meiotic division. Other modes of origin (true polyploidy, accidental superposition of cells during preparation) were unlikely. The data could be accommodated by a statistical model with only four parameters. It allowed for artifactual fusion mainly between daughter cells but also between non-daughter cells, bias in one scoring method, and bias in the numbers of cells with given ploidy successfully mounted. Current techniques of chromosome preparation were thought to be wholly unsuitable for the recognition of true polyploidy. The artifactual origin of polyploid spreads was borne out by an absence of polyploid spermatozoa in 14 strains. There appeared to be a virtually constant transmission rate of paternal X and Y chromosomes from early meiosis to late blastocyst. The estimated rate of 49.05+/-0.67% with a Y chromosome also estimated the primary sex ratio. There was evidence of polymorphism in autosomal pericentromeric staining in 3 strains. No measure of the numbers of autosomes or sex chromosomes varied significantly between duplicate preparations or between duplicate males of a strain.
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