Electrophoretic Evidence for Genetic Diploidy in the Bracken Fern (Pteridium aquilinum).

Analysis of isozyme variability demonstrates that bracken fern (Pteridium aquilinum) has a diploid genetic system and expresses solely disomic inheritance patterns. Electrophoretic data indicate that genetically variable progeny are produced in natural populations after intergametophytic mating rather than by a process involving recombination between duplicated unlinked loci. Although some enzymes are encoded by more than one locus, this has resulted from subcellular compartmentalization of isozymes, and there is no evidence of extensive gene duplication resulting from polyploidy. The conclusions reached in this report differ from those which propose polyploidy as an adaptive mechanism for maintaining genetic variability in Pteridium and other homosporous pteridophytes.

Characterization of the insulin-like growth factor axis and Wilms' tumour suppressor gene in hyperparathyroidism.

BACKGROUND: Genetic mutations and upregulation of growth factors are implicated in the pathogenesis of hyperparathyroidism. The aim of this study was to evaluate the role of Wilms' tumour suppressor gene (WT-1) and the insulin-like growth factor (IGF) axis in hyperparathyroidism. METHODS: The expression of WT-1 and IGF components was examined by immunohistochemistry, reverse transcriptase-polymerase chain reaction and western immunoblotting in a panel of parathyroid specimens from both primary and secondary hyperparathyroidism. A human parathyroid cell culture model was established to examine the parathyroid response to IGF stimulation. RESULTS: There was a significantly lower level of WT-1 expression in parathyroid tumours than in normal parathyroid glands. Most tumours expressed IGF-I and IGF-II receptors and responded to IGF stimulation. Only IGF-I was present in normal parathyroid glands, whereas IGF-II was expressed exclusively in parathyroid tumours. CONCLUSION: Abnormal expression of WT-1 and the IGF axis may play a role in the pathogenesis of hyperparathyroidism.

Upregulation of surface alpha4beta2 nicotinic receptors is initiated by receptor desensitization after chronic exposure to nicotine.

It is hypothesized that desensitization of neuronal nicotinic acetylcholine receptors (nAChRs) induced by chronic exposure to nicotine initiates upregulation of nAChR number. To test this hypothesis directly, oocytes expressing alpha4beta2 receptors were chronically incubated (24-48 hr) in nicotine, and the resulting changes in specific [3H]nicotine binding to surface receptors on intact oocytes were compared with functional receptor desensitization. Four lines of evidence strongly support the hypothesis. (1) The half-maximal nicotine concentration necessary to produce desensitization (9.7 nM) was the same as that needed to induce upregulation (9.9 nM). (2) The concentration of [3H]nicotine for half-maximal binding to surface nAChRs on intact oocytes was also similar (11.1 nM), as predicted from cyclical desensitization models. (3) Functional desensitization of alpha3beta4 receptors required 10-fold higher nicotine concentrations, and this was mirrored by a 10-fold shift in concentrations necessary for upregulation. (4) Mutant alpha4beta2 receptors that do not recover fully from desensitization, but not wild-type channels, were upregulated after acute (1 hr) applications of nicotine. Interestingly, the nicotine concentration required for half-maximal binding of alpha4beta2 receptors in total cell membrane homogenates was 20-fold lower than that measured for surface nAChRs in intact oocytes. These data suggest that cell homogenate binding assays may not accurately reflect the in vivo desensitization affinity of surface nAChRs and may account for some of the previously reported differences in the efficacy of nicotine for inducing nAChR desensitization and upregulation.

Best practice no 183. Examination of parathyroid gland specimens.

The pathological examination of parathyroid glands is an essential component of the evaluation of hyperparathyroidism. Traditionally, this has involved intraoperative frozen sections during bilateral surgical exploration of the neck, to confirm removal of parathyroid tissue. With recent developments in imaging, some diseased glands can be localised preoperatively, enabling removal by minimally invasive, targetted surgery, with or without additional non-histological intraoperative procedures to confirm the removal of all hyperfunctioning parathyroid tissue. This article reviews these developments and describes the ideal approach to reporting parathyroid specimens.

Histopathological changes in the human larynx following expanded polytetrafluroethylene (Gore-Tex(R)) implantation.

BACKGROUND: Expanded polytetrafluroethelyne (e PTFE, Gore-Tex(R)) has been advocated as an implant material for medialization of the vocal fold. Animal studies involving rabbits and a porcine model have demonstrated host tolerance of the implant. There have been no reports describing the histological changes in a human laryngectomy specimen with a Gore-Tex implant. CASE PRESENTATION: The histological findings in a laryngectomy specimen of a patient previously implanted with e PTFE for medialization of a paralyzed vocal fold following excision of a vagal neurofibroma were studied.Histopathology revealed a mild foreign-body giant cell granulomatous reaction with some associated fibrosis. The granulomatous response was limited to the periphery of the Gore-Tex and although it closely followed the profile of the material it did not encroach into or significantly break up the material. There was no significant neutrophilic or lymphocytic inflammation. CONCLUSIONS: Our findings are consistent with the animal models confirming that Gore-Tex implantation does not result in a significant granulomatous reaction in the human larynx over a 13-month period. Moreover, there is no evidence of resorption or infection. Further, the lack of lymphocytes in association with the granulomas indicates that there is no significant immunological hypersensitivity. Histologically, the slight permeation by connective tissue is similar to that seen in Gore-Tex vascular and cardiac implants. The degree of the slight giant cell response appears to be dependent on the profile of the material; a sharp edge incited more of a response than a flat surface.

Nicotinic acetylcholine receptor subunit mRNA expression and channel function in medial habenula neurons.

Relationships between nicotinic acetylcholine receptor (nAChR) channel function and nAChR subunit mRNA expression were explored in acutely isolated rat medial habenula (MHb) neurons using a combination of whole-cell recording and single cell RT-PCR techniques. Following amplification using subunit-specific primers, subunits could be categorized in one of three ways: (i) present in 95-100% cells: alpha3, alpha4, alpha5, beta2 and beta4; (ii) never present: alpha2; and (iii) sometimes present ( approximately 40% cells): alpha6, alpha7 and beta3. These data imply that alpha2 subunits do not participate in nAChRs on MHb cells, that alpha6, alpha7 and beta3 subunits are not necessary for functional channels but may contribute in some cells, and that nAChRs may require combinations of all or subsets of alpha3, alpha4, alpha5, beta2 and beta4 subunits. Little difference in the patterns of subunit expression between nicotine-sensitive and insensitive cells were revealed based on this qualitative analysis, implying that gene transcription per se may be an insufficient determinant of nAChR channel function. Normalization of nAChR subunit levels to the amount of actin mRNA, however, revealed that cells with functional channels were associated with high levels (>0.78 relative to actin; 11/12 cells) of all of the category (i) subunits: alpha3, alpha4, alpha5, beta2 and beta4. Conversely, one or more of these subunits was always low (<0.40 relative to actin) in all cells with no detectable response to nicotine. Thus the formation of functional nAChR channels on MHb cells may require critical levels of several subunit mRNAs.

Adaptations to extreme low light in the fern Trichomanes speciosum.

Trichomanes speciosum is a threatened species restricted to sheltered, very humid sites. Uniquely amongst European ferns, differing ecological tolerances of the gametophyte and sporophyte generations are manifested as widely differing distributions. The perennial, vegetatively propagating gametophyte persists in drier, colder, darker habitats than the sporophyte. In sites where the gametophyte grows, light availability was found to be < 1 µmol m2 s1 for approx. 85% of daylight hours, rarely or (in some sites) never rising above 10 µmol m2 s1 . Much of the time, light was < 0.01% of full sunlight. Measurements of gas exchange and chlorophyll fluorescence yield show that these plants have optimal photosynthesis at light intensities c. 5-10 µmol m2 s1 , the highest light to which they are normally exposed to in their natural environment. The absence of any capacity for reversible nonphotochemical fluorescence quenching means that there is little or no protection of the photosynthetic apparatus from light-induced damage. We conclude that these plants are able to create what are essentially monocultures in their extreme environments only because of a combination of low metabolic rate (at low temperatures) and an ability to make efficient use of what little light is available to them by morphological and physiological means.

Contrasting strategies for UV-B screening in sub-Arctic dwarf shrubs.

The content and distribution of UV-absorbing phenolic compounds was investigated in leaves of three species of Vaccinium co-existing at a site in north Sweden. Vaccinium myrtillus L., Vaccinium vitis-idaea L., and Vaccinium uliginosum L. exhibit markedly different strategies, in terms of localization and content of leaf phenolics and in their responses to UV-B enhancement. Plants were exposed to either ambient radiation or to enhancement of UV-B corresponding to 15% (clear sky) depletion of stratospheric ozone for approximately 10 years prior to commencement of this study. Vaccinium myrtillus contained the highest concentration of methanol-extractable UV-B-absorbing compounds, which was elevated in plants exposed to enhanced UV-B. Fluorescence and confocal laser scanning microscopy showed that these compounds were distributed throughout the leaf, and were particularly concentrated in chlorophyll-containing cells. In V. vitis-idaea, most phenolic compounds were cell wall-bound and concentrated in the walls of the epidermis; this pool increased in response to UV-B enhancement. It is suggested that these two plants represent extreme forms of two divergent strategies for UV-B screening, the different responses possibly being related to leaf longevity in the two species. The response of V. uliginosum was intermediate between the other two, with high concentrations of cell wall-bound phenolics in the epidermis but with this pool decreasing, and the methanol-soluble pool tending to increase, after exposure to enhanced UV-B. One explanation for this response is that this plant is deciduous, like V. myrtillus, but has leaves that are structurally similar to those of V. vitis-idaea.

Epithelial hyperplasia and malignant change in congenital lung cysts.

Patients with congenital lung cysts are at increased risk of developing carcinoma, but the mechanisms concerned are not clear. The case of a young adult who developed a bronchioloalveolar carcinoma associated with a cystic congenital adenomatoid malformation is reported. The adjacent lung showed an unusual intra-alveolar hyperplasia of mucous cells. Two further cases of congenital adenomatoid malformation are also described; both patients presented in infancy and showed similar mucous cell hyperplasia in alveoli surrounding the cysts. In all three cases the staining characteristic of the mucus was identical with that of normal bronchial mucous glands. It is suggested that the benign proliferation represents a premalignant lesion. Its presence in infants shows that it may occur at an early age and reinforces the need for early removal of congenital lung cysts.

Measurement of vascularity as a diagnostic and prognostic tool for well differentiated thyroid tumours: comparison of different methods of assessing vascularity.

AIMS: To determine whether the measurement of vascularity can be used to differentiate follicular adenomas from follicular carcinomas or to reflect the prognosis of follicular carcinomas and papillary carcinomas of the thyroid gland, and to compare four methods of assessing vascularity. METHODS: Tissue sections from 26 papillary carcinomas, 15 follicular adenomas, and 15 follicular carcinomas were stained with an antibody to CD34. A computerised image analysis system was used to calculate, for each tumour, mean endothelial areas and the mean endothelium to tumour epithelial nucleus area ratio from 10 systematically selected fields across one dimension of the tumour ("systematic field" analysis) or from the three most vascularised fields of the tumour ("hot spot" analysis). A European Organisation for Research on Treatment of Cancer (EORTC) prognostic index was calculated for each papillary carcinoma and follicular carcinoma. RESULTS: Significant differences in vascularity between the three tumour groups could only be shown by comparing mean endothelial area values measured from hot spots. While the hot spot median mean endothelial area of follicular carcinomas was significantly greater than that of follicular adenomas, there was a large overlap between the two groups. For follicular carcinomas, higher hot spot mean endothelial area values were related to worse prognosis as indicated by the EORTC prognostic indices. No association between vascularity and prognosis was found for the papillary carcinomas, regardless of the method of assessing vascularity. CONCLUSIONS: Measuring endothelial area from hot spots using a computerised image analysis system is a sensitive method of assessing the vascularity of thyroid tumours. While vascularity measurement cannot be recommended as a practical tool for differentiating between malignant and benign follicular tumours, the suggestion that vascularity may reflect prognosis for follicular carcinomas deserves further study.

An unusual case of colonic angiodysplasia.

An unusual case of a colonic vascular anomaly resembling angiodysplasia associated with right sided diverticular disease is presented. The patient, a 74 year old man, presented with a four day history of rectal bleeding and subsequently underwent hemicolectomy. The resected specimen was flushed out with heparin-saline solution and injected with a barium-gelatine mixture. Preoperative barium enema revealed right sided diverticula, whereas post-resection angioradiography revealed the "coral reef" vascular anomaly consistent with angiodysplasia. Histology confirmed the presence of both diverticular disease and angiodysplasia. This case report highlights the importance of considering a vascular anomaly in patients presenting with rectal bleeding despite the presence of another radiologically demonstrable anatomical lesion.

Age changes at cerebral artery bifurcations and the pathogenesis of berry aneurysms.

Cerebral artery bifurcations with and without aneurysms were studied in postmortem brains by histology (1-micron resin sections) and by scanning electron microscopy. Specimens were taken from 20 patients without aneurysms with an age range of 1 month--80 years. Gaps in the tunica media at the carina and the lateral wall of the bifurcations were observed in 60% of specimens from arteries at all ages, but they were larger in older patients. A more striking change with age was the development of inelastic pads of intimal thickening in relation to bifurcations. Intimal pads were observed at and distal to the carina of bifurcations, but scanning electron microscopy also revealed intimal pads proximal to bifurcations in 60% of patients over the age of 30 years and in 2 out of 9 (22%) patients under 10 years. Similar pads covered a much wider area of vessel wall proximal to the necks of berry aneurysms in the 15 patients studied. Contralateral bifuractions in these patients showed no difference from non-aneurysm patients. It is suggested that the inelastic intimal pads form as a result of haemodynamic stress and that the presence of such pads may alter the stresses and strains at vessel bifurcations. Together with the presence of a gap in the tunica media, the pattern of inelastic intimal pad formation may be a major predisposing factor in the formation of cerebral artery aneurysms.

Pathology of sarcoidosis.

This article reviews the pathology of sarcoidosis that covers the general and systemic aspects of the disease. Macroscopic and microscopic descriptions of the disease process are given for selected organs.

Anomalous origin of single coronary artery in association with pulmonary atresia.

We report a case of pulmonary atresia with intact septum associated with single coronary artery which originated from the pulmonary trunk. The combination of stenotic pulmonary trunk with presence of right ventricular to coronary artery fistulous connections probably impaired myocardial perfusion after birth.

Early diagnosis of subependymal giant cell astrocytoma in patients with tuberous sclerosis.

We present 19 patients with tuberous sclerosis complex and subependymal giant cell astrocytoma. The mean age at the time of tumor diagnosis was 9.4 years (range, 1.5 to 21 years). Computed cranial tomography (CT) or cranial magnetic resonance imaging (MRI) identified the lesion which was resected in all cases. Seven patients had hydrocephalus and there was an interval increase in the tumor size or a large tumor without hydrocephalus in 12 patients. Surgical criteria included: (1) presence of hydrocephalus; (2) interval increase in tumor size; (3) new focal neurologic deficit attributable to the tumor; and/or (4) symptoms of increased intracranial pressure. Eight patients were identified through a surveillance program involving annual computed cranial tomography. All of these eight patients had their tumor removed prior to the development of symptoms, none had neurologic deficits which persisted after surgery, and none has so far developed recurrent subependymal giant cell astrocytoma. In contrast, of the 11 patients from the non-surveillance group 7 were symptomatic at tumor diagnosis, 1 had a complicated postoperative course, 2 developed recurrent giant cell astrocytoma, and 1 had an extensive lesion that could not be completely excised. Periodic cranial imaging may help to identify subependymal giant cell astrocytomas in tuberous sclerosis patients before they become symptomatic. Earlier diagnosis and treatment could reduce surgical morbidity and the risk of tumor recurrence.

Growth and development of fern gametophytes in an airlift fermenter.

Spores of the fernsPteridium aquilinum andAnemia phyllitidis were grown in an airlift fermenter and subsequent growth and development of gametophytes was monitored. Both species produced greater biomass than that generated in any other solid- or liquid-based culture system tested.Pteridium generated more tissue thanAnemia in every system. The morphology of airlift-grown gametophytes was similar to that of soil-grown plants; fewer gametophytes with perturbed development were observed in airlift cultures than in the other liquid-based systems. No attempt was made to optimise airlift conditions for the species and tissue employed, so it is concluded that airlift cultivation is a promising system for the bulk production of fern gametophytic tissue.

Reproducibility in the measurement of atlanto-occipital instability in children with Down syndrome.

STUDY DESIGN: This study compared the reproducibility of three techniques used to measure translation between the occiput and C1 in children with Down syndrome. OBJECTIVES: Intraobserver and interobserver variability were computed to determine if there is a reliable way to measure occiput-C1 instability. SUMMARY OF BACKGROUND DATA: No studies have been performed comparing measurement techniques in children with Dow syndrome. METHODS: Powers ratios, basion-axial intervals, and translational anteroposterior motion as described by Wiesel and Rothman were calculated for 50 pairs of flexion-extension lateral cervical radiographs from children with Down syndrome. Calculations were made on two occasions by four reviewers. RESULTS: Mean differences between measurements for two observers were 0.14 for the Powers ratio, 1.3 mm for the Wiesel technique, and 1.8 mm for the basion-axial interval. The 95th percentiles of the differences between measurements for two observers were 0.38 for Powers ratios, 3.5 mm for the Wiesel technique, and 5.3 mm for the basion-axial interval. CONCLUSIONS: Measurement of atlanto-occipital translation by any of these methods is not reproducible. Although the technique by Wiesel and Rothman is the easiest to apply, confirmation of instability with magnetic resonance imaging should guide management.

Protein C deficiency associated with massive cerebral thrombosis following open heart surgery.

We describe a case of massive cerebral venous thrombosis following open heart surgery in a patient with a reduced level of Protein C (40% of mean level). Protein C deficiency is an inherited disorder which in the homozygous form may result in massive fatal venous thrombosis in the newborn. A Protein C level below 55% is highly suggestive of heterozygous deficiency and has been associated with a tendency to venous thrombosis although its clinical penetrance is variable. This is the first reported case of massive venous thrombosis in a patient following open heart surgery associated with Protein C deficiency.

Imprint cytology of parathyroid tissue in relation to other tissues of the neck and mediastinum.

OBJECTIVE: To retest the hypothesis that imprint cytology may be used to reliably diagnose parathyroid tissue and, if so, to ascertain whether accuracy in this technique may be easily attained. STUDY DESIGN: Imprint preparations from 15 parathyroid, 10 thyroid, 8 lymphoreticular and 2 adipose tissue specimens were assessed blindly by two pathologists, one of whom (pathologist B) had only limited experience with endocrine tissue imprint cytology. RESULTS: Both assessors consistently distinguished parathyroid and thyroid preparations from lymphoreticular and adipose tissue preparations. While there was occasional difficulty in distinguishing between parathyroid and thyroid preparations, this was usually attributable to the scanty nature of the preparations. No single cytologic feature allowed a distinction between parathyroid and thyroid tissue. However, by considering several relatively diagnostic features collectively, pathologist B showed an increase in specificity and sensitivity rates for distinguishing parathyroid from thyroid imprints from 82% to 100% and 57% to 83%, respectively. CONCLUSION: The high accuracy rates and rapid [table: see text] learning curve shown by imprint cytology in distinguishing between different neck or mediastinal tissue types, together with its time- and cost-cutting potential, support a role for the technique in the intraoperative diagnosis of parathyroid tissue.

Low grade marginal zone B-cell lymphoma presenting as local amyloidosis in a submandibular salivary gland.

An unusual case of a low grade marginal zone B-cell lymphoma is reported and the literature reviewed. This case demonstrates that a diagnosis of lymphoma must be considered when there is amyloidosis in an otherwise asymptomatic submandibular salivary gland mass.