Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

Tessellated calcified cartilage (TCC) is a distinctive kind of biomineralized perichondral tissue found in many modern and extinct chondrichthyans (sharks, rays, chimaeroids and their extinct allies). Customarily, this feature has been treated somewhat superficially in phylogenetic analyses, often as a single "defining" character of a chondrichthyan clade. TCC is actually a complex hard tissue with numerous distinctive attributes, but its use as a character complex for phylogenetic analysis has not yet been optimized. This study attempts to improve this situation by presenting new terminology for certain aspects of tesseral architecture, including single-monolayered, multiple-monolayered, polylayered and voussoir tesserae; new histological data, including thin sections of TCC in several Palaeozoic taxa, and new proposals for ways in which various characters and states (many of which are defined here for the first time) could be applied in future phylogenetic analyses of chondrichthyan fishes. It can be concluded that many, but not all, of the unique attributes of modern TCC evolved by the Early Devonian (ca. 400 before present (bp)). The globular calcified cartilage reported in Silurian sinacanthids and the so-called subtessellated perichondral biomineralization (with irregular and ill-defined geometries of a layer or layers of calcified cartilage blocks) of certain extinct "acanthodians" (e.g., Climatius, Ischnacanthus, Cheiracanthus) could represent evolutionary precursors of TCC, which seems to characterize only part of the chondrichthyan total group. It is hypothesized that heavily biomineralized "layer-cake" TCC in certain Palaeozoic chondrichthyans perhaps served a dual physiological role, as a phosphate sink and in providing increased skeletal density in very large (>7 m) Devonian-Permian marine sharks such as ctenacanths and as an adaptation to calcium-deficient environments among Permo-Carboniferous non-marine sharks such as xenacanths. By contrast, the equivalent tissue in modern elasmobranchs probably serves only to reinforce regions of cartilage (mostly in the jaws) subjected to high loading. It is also noted that much of the variation observed in tesseral architecture (including localized remodelling), ultrastructure and histology in modern and extinct chondrichthyans is confined to the perichondrally facing cap zone (where Type-1 collagen matrix predominates in modern TCC), whereas the main body of the tessera (where Type-2 collagen matrix predominates) exhibits comparatively little evidence of remodelling and histological or structural variation.

Estrogen inhibits sphincter of Oddi motility

Gallstones and sphincter of Oddi dysfunction are both more common in women than men, suggesting that endogenous hormones may play an important role in these conditions. Female sex hormones are known to affect cholesterol metabolism and gallbladder motility. However, the effect of these hormones on the sphincter of Oddi has not previously been studied. We therefore tested the hypothesis that exogenous estrogen administration would inhibit sphincter of Oddi motility. Twenty-three male prairie dogs fed a nonlithogenic diet were studied. Under alpha-chloralose anesthesia, a side hole pressure-monitored perfusion catheter was positioned in the sphincter of Oddi and perfused with degassed water at 0.15 ml/min. Femoral arterial and venous catheters were placed. Sphincter of Oddi phasic wave frequency (F), amplitude (A), and motility index (MI = F x A), as well as arterial blood pressure (BP), were monitored for 10-min intervals before (control), during 20-min intravenous infusions of 0.1, 1, or 10 micrograms/kg beta-estradiol, and for 20 min after estradiol infusion. No response was observed at the 0.1- or 1-micrograms doses. Sphincter of Oddi motility was significantly (P < 0.05) reduced during estrogen infusion at the higher dose of 10 micrograms, primarily due to decreased phasic wave frequency. Sphincter motility remained depressed for at least 20 min following estrogen infusion. We conclude that estrogen effects on the sphincter of Oddi may contribute to the higher incidence of gallstones and sphincter dysfunction seen in premenopausal women.

STK-1, the human homolog of Flk-2/Flt-3, is selectively expressed in CD34+ human bone marrow cells and is involved in the proliferation of early progenitor/stem cells

We cloned the cDNA for stem cell tyrosine kinase 1 (STK-1), the human homolog of murine Flk-2/Flt-3, from a CD34+ hematopoietic stem cell-enriched library and investigated its expression in subsets of normal human bone marrow. The cDNA encodes a protein of 993 aa with 85% identity and 92% similarity to Flk-2/Flt-3. STK-1 is a member of the type III receptor tyrosine kinase family that includes KIT (steel factor receptor), FMS (colony-stimulating factor 1R), and platelet-derived growth factor receptor. STK-1 expression in human blood and marrow is restricted to CD34+ cells, a population greatly enriched for stem/progenitor cells. Anti-STK-1 antiserum recognizes polypeptides of 160 and 130 kDa in several STK-1-expressing cell lines and in 3T3 cells transfected with a STK-1 expression vector. Antisense oligonucleotides directed against STK-1 sequences inhibited hematopoietic colony formation, most strongly in long-term bone marrow cultures. These data suggest that STK-1 may function as a growth factor receptor on hematopoietic stem and/or progenitor cells.

Small bowel infarction in association with giant cell arteritis

Giant cell arteritis is not uncommonly found in extracranial arteries in postmortem studies of patients with temporal arteritis. Presentation with vasculitis involving extracranial arteries is, however, unusual. This report describes a case of giant cell arteritis presenting with and complicated by infarction of the small bowel. Following surgical resection of the infarcted segment of bowel and commencement of steroid therapy, the patient is now well and free of symptoms. The literature concerning extracranial and in particular small bowel giant cell arteritis is reviewed.

Percutaneous transcatheter recanalization in the management of acute renal failure due to sudden occlusion of the renal artery to a solitary kidney

Percutaneous angioplasty was attempted in 5 patients with acute renal failure due to occlusion of the artery to a solitary functioning kidney. Angioplasty was technically successful in all patients. Renal function was completely restored in 3 and renal perfusion improved in 1 patient. In the fifth patient, renal function did not return despite ultrasound and radionuclide scan evidence of renal reperfusion. Transcatheter thrombolytic therapy was attempted in 2 patients, 1 of whom also underwent angioplasty. In this patient, perfusion was restored to most of the kidney. In the other patient an infrarenal aortic occlusion was present. During thrombolytic therapy, intrarenal microembolization occurred from lysis of the aortic thrombus, leading to irreversible renal damage.

Pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease has recently been recognized as a distinct pathological entity and a cause of pulmonary arterial hypertension. Twenty previously reported cases and a new patient are here reviewed. The majority presented with breathlessness and in the early stages of the disease, when the abnormal signs were not striking, some patients were wrongly diagnosed as suffering from an anxiety state. The condition usually has an insidious onset but is remorselessly progressive and since no effective treatment is available at present, invariably fatal and the majority of patients have died within two years. The fully developed clinical picture is dominated by symptoms and signs of pulmonary arterial hypertension, similar to those found with other diseases causing a raised pulmonary arterial blood pressure. However, some patients with pulmonary veno-occlusive disease show, in addition, signs of pulmonary venous and capillary hypertension, which can lead to its clinical recognition when associated with a normal left atrial blood pressure. In this condition the pulmonary wedge pressure would appear to be unreliable as a record of the left atrial blood pressure. Pulmonary angiography and lung scanning will differentiate pulmonary veno-occlusive disease from massive thromboembolic pulmonary arterial hypertension but not from primary pulmonary arterial hypertension or micro thromboembolism. Although in some patients it should now be possible to recognise pulmonary veno-occlusive disease in life, there will be others where, even after full investigation, it will still be impossible to differentiate the condition from primary pulmonary arterial hypertension or micro thromboembolism and in these the diagnosis will only be made when the distinctive histological pattern of the disease is demonstrated. In pulmonary veno-occlusive disease there is a widespread occlusion of the pulmonary veins and venules by a loose intimal fibrosis which is often basophilic. Recanalization of the occluded veins is common and in some cases may be very striking. These occlusive lesions in the pulmonary veins lead to an elevation of pulmonary arterial pressure with associated disease of these vessels, and are also responsible for chronic oedema of the elveolar walls with subsequent development of interstitial pulmonary fibrosis. In the present case organised thrombi were present in the pulmonary arteries in addition to the pulmonary venous lesions.