Biomedical subjects
J R Meyer
Publications and source records attributed to J R Meyer.
Osteochondroma of the thoracic spine: an unusual cause of spinal cord compression.
A 24-year-old man with hereditary multiple exostoses had numbness of the lower extremities and difficulty walking. CT displayed a calcified extradural mass lesion within the spinal canal at T-8 causing cord compression. MR imaging showed it to be contiguous with the upper endplate of T-8, suggesting the diagnosis of osteochondroma, a rare cause of cord compression, and distinguishing the lesion from a calcified disk fragment.
Adult-onset presentation of Dandy-Walker variant in siblings.
BACKGROUND: The Dandy-Walker syndrome and Dandy-Walker variant usually present as isolated cases of hydrocephalus in pediatric patients. METHODS AND RESULTS: THis paper consists of a case report of the adult onset of symptoms in two sisters having Dandy-Walker variant. Such an occurrence has never before been reported in the medical literature. Both patients presented with headaches and progressive neurologic deficit. On computed tomography (CT scan) of the head, both were found to have hydrocephalus, with hypoplasia of the inferior vermis. Both patients were treated successfully with ventriculoperitoneal shunting. A third sister, with a similar history, elected not to undergo CT scanning or surgical treatment. CONCLUSIONS: Variants of the Dandy-Walker syndrome may occasionally present clinically in the adult age group. Such an occurrence in siblings is consistent with an underlying genetic etiology.
Giant Rathke cleft cyst.
The preoperative diagnosis for an unusual skull base lesion was chordoma. The combination of imaging, pathologic, and surgical findings suggests the diagnosis of Rathke cyst.
Flare response in Ewing's sarcoma.
A 3 1/2-year-old boy had thigh pain and a leg mass. Bone scanning demonstrated intense uptake within the involved femur, but no uptake within the soft tissues or evidence of metastatic spread. Radiographs and CT scanning showed a large soft tissue mass and periosteal reaction suggestive of Ewing's sarcoma. Following chemotherapy, the patient had an apparently good clinical response. However, bone scanning showed uptake that was more intense and extensive than it was before therapy. Plain films and CT showed that the uptake was evidence of soft tissue calcification and that the mass had shrunk. This is an unusual example of the flare response to therapy because the apparent progression of the disease on bone scanning was caused by extraskeletal uptake.
Potassium-induced release of endogenous glutamate and two as yet unidentified substances from the lateral line of Xenopus laevis.
The release of endogenous glutamate and other primary amines from the lateral-line of Xenopus laevis was studied using an in vitro superfusion technique and high performance liquid chromatography. Potassium stimulation (50 mM KCl) applied to 60 or 120 lateral-line organs dissected from the skin and pooled in a perfusion chamber induced the release of glutamate and aspartate. The release of aspartate was smaller than that of glutamate and more variable. A variable release of two, as yet, unidentified substances was also detected. In low calcium (0.1 mM CaCl2), high magnesium (10 mM MgCl2) solution, 50 mM potassium failed to induce an increase in glutamate, aspartate and the two unknowns, suggesting they are released in a transmitter-like manner. The technique presents a new and simple method for studying transmitters in hair-cell systems. Although other interpretations are possible, the results are consistent with the hypothesis that glutamate is a hair-cell transmitter and suggest a potential role for other substances in the transduction process, perhaps as neuromodulators.
Hypercoagulable states and lower limb ischemia in young adults.
This study prospectively evaluates hypercoagulable states in patients under 51 years of age undergoing lower extremity revascularization for ischemia and assesses early outcome after operation. Twenty patients whose ages range from 23 to 50 years (mean 40.8 years) were identified prospectively who underwent lower extremity revascularization and evaluation of hypercoagulability. Fifteen patients were male (75%), 10 were black (50%), six had hypertension (30%), and four were diabetic (20%). All but two were cigarette smokers (90%). Seven aortoiliac procedures and 13 infrainguinal procedures were performed. Six patients had one or more abnormalities of regulatory proteins (protein S deficiency, four; protein C deficiency, three; presence of lupus-like anticoagulant, three; plasminogen deficiency, two). Eight of 17 patients in whom platelet aggregation profiles were obtained showed increased reactivity (47%). Only 4 of 17 patients (24%) were normal when tested for all parameters. Arterial or graft thrombosis developed in four of the 20 patients within 30 days after operation. Hypercoagulability was found in all four patients whose revascularizations failed. A high incidence of hypercoagulable states was found in patients under 51 years of age with lower limb ischemia requiring revascularization. Hypercoagulability may have contributed to early postoperative thrombosis of the vascular procedure.
Preliminary pharmacokinetics of ketoconazole in gopher tortoises (Gopherus polyphemus).
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Kaposi's sarcoma in AIDS: basement membrane and endothelial cell markers in late-stage lesions.
Early-stage lesions of Kaposi's sarcoma (KS) are composed of single-layered, highly flattened cells lining collagen bundles, whereas late-stage lesions contain densely packed, spindle-shaped cells. We examined the progression of KS lesions in oral mucosa and lymph nodes from patients with AIDS, using antibodies specific for blood vascular endothelial cells (Factor VIII-related antigen) and their basement membrane (Type IV collagen and laminin). In addition, the plant lectin Ulex europaeus, which selectively stains blood vessels, was also used. In early-stage KS lesions, fibronectin, laminin and Type IV collagen were co-distributed at the interface between KS cells and collagen bundles; Factor VIII-related antigen and Ulex europaeus lectin staining was present in vascular channels and in the KS cells. However, in late-stage lesions, few if any KS cells stained with antibody to Factor VIII-associated antigen, although endothelial cells lining blood vessels were positive. Strong staining for laminin and Type IV collagen was present in a pericellular pattern throughout the nodular late-stage lesions. Since lymphatic capillary endothelium does not produce basement-membrane-specific macromolecules, these results support the conclusion that KS cells are related to blood vascular endothelium but eventually lose certain endothelium-specific markers as the cells are transformed into the spindle-shaped cell type.
The regenerative potential of the periodontal ligament.
The current decline in the incidence of dental caries indicates that patients will retain most of their dentition. Reconstruction or regeneration of the entire attachment apparatus, including the periodontal ligament, cementum, and bone, is an attainable therapeutic goal. Clinical treatments designed to reattach connective tissue to exposed root surfaces commonly result in the formation of a long junctional epithelial attachment. This attachment is probably not an effective barrier to bacterial toxins and may allow recurrent pocket formation. To enhance reattachment of connective tissue, root-conditioning agents have been used but their clinical efficacy is questionable. Restoration of destroyed alveolar supporting bone by means of allogenic and autogenous bone-grafting materials has been recommended, but these procedures do not restore the cementum and PDL. Attempts to promote regeneration of the entire attachment apparatus have included clinical studies that used mechanical means to promote repopulation of affected root surfaces by periodontal ligament fibroblasts and prevent contact of epithelial or gingival connective tissue cells. Results thus far have been encouraging, but the practicality of these techniques may be limited. However, these studies have demonstrated that if only PDL cells contact the root surface during healing, a normal PDL can re-form. Dental follicle tissue is capable of inducing the formation of cementum-like structures and is clearly the cell population responsible for cementum and PDL formation. Recent research has demonstrated that the dental papilla probably shares the same inductive capabilities as the dental follicle.(ABSTRACT TRUNCATED AT 250 WORDS)
Histologic evaluation of a human periapical defect after implantation with tricalcium phosphate.
This case report describes the effect of tricalcium phosphate implantation in the treatment of a chronic periapical abscess. Ceramic implant materials are biocompatible and are currently being used to restore alveolar bone loss resulting from periodontal disease, endodontic infections, and residual alveolar ridge resorption. However, use of such a material in this case led to persistent infection and additional bone destruction. Thus, the use of a ceramic implant material to accelerate periapical bone repair is not recommended in areas where a chronic bacterial infection is present.
Localization of basement membrane components in mucous membrane pemphigoid.
We examined the distribution of laminin, type IV collagen, and fibronectin in subepithelial vesicles of oral mucous membrane pemphigoid (MMP). Indirect immunofluorescence staining of these macromolecules was performed on 10 frozen biopsy specimens of oral MMP. We found type IV collagen in the connective tissue floor and laminin in the epithelial roof of these lesions. Our results suggest that the inflammatory injury in oral MMP may disrupt the interaction of laminin with type IV collagen in the basement membrane zone.
Distribution of fibronectin and laminin in oral leukoplakia and carcinoma.
We determined the distribution of 2 components of the extracellular matrix, fibronectin and laminin, in normal, premalignant, and malignant oral mucosa. Both indirect immunofluorescence and avidin-biotin complex immunoperoxidase techniques were used with antisera to each glycoprotein. Fibronectin was consistently present in the basement membrane and connective tissue of normal, leukoplakic and malignant oral mucosa regardless of anatomic site. A continuous laminin-reactive basement membrane structure separated tumor parenchyma from the associated stroma except in areas of invasion in which no laminin staining was evident.
Abomasal impaction in sheep.
Abomasal engorgement was diagnosed in five Suffolk rams and one Suffolk ewe. All sheep had poor or no appetite for between seven days and five months duration. They were depressed, thin and weak. Rectal temperature and respiration rates were within the normal range. Pulse rate was increased (97.6 +/- 11.55/minute, mean +/- se). A distended abdomen was present and, or, a firm mass was ballotted or palpated in the lower right abdomen. Rumen motility was increased and contractions were strong. Laparotomy revealed enlarged abomasums in four sheep. Enlarged abomasums were found at necropsy in two sheep. Abomasal contents resembled rumen ingesta in character and odour. Removal of ingesta by abomasotomy produced temporary improvement in three rams for six to 12 weeks. All six sheep died or were euthanased.
Hypoxic ventilatory depression in dogs.
It is well known that hypoxia, acting mainly through peripheral chemoreceptors, is an important ventilatory stimulus. It is also known that under certain circumstances hypoxia can lead to ventilatory depression, perhaps through its effect on the central nervous system. This study, utilizing dogs, was carried out to determine the degree of hypoxia required to produce ventilatory depression and to study the effects of chloralose anesthesia, variations in blood carbon dioxide tension, and peripheral chemoreceptor denervation on hypoxic ventilatory depression. In the awake, intact dog, ventilatory depression did not occur until the Pao2 = 18.6 plus or minus 0.8 mmHg (SEM). This value was not significantly different from that observed in chloralose anesthetized dogs, Pao2 = 18.7 plus or minus 0.43 mmHg. Hyper- and hypocapnia had no significant effect on the Pao2 at which ventilatory depression occurred. Denervation of either aortic or carotid chemoreceptors produced a very small change in the Pao2 of ventilatory depression, increasing it from 18.6 plus or minus 0.58 to 20.8 plus or minus 0.93 mmHg. Denervation of both aortic and carotid chemoreceptors produced a further small increase (Pao2 = 21.8 plus or minus 0.76 mm Hg). In peripheral chemoreceptor-denervated animals, hypoxia produced no significant change in ventilation until the ventilatory depression point was reached. These studies indicate that in the dog hypoxic ventilatory depression occurs only during severe hypoxia and ventilatory depression occurs only during severe hypoxia and is uninfluenced by chloralose anesthesia, hyper- or hypocapnia, and only slightly affected by chemoreceptor denervation.
Environmental modification of Rana pipiens sciatic nerve function.
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A new approach to quantitation of whole nerve bundle activity.
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Environmental modification of sciatic nerve conduction velocity in Rana pipiens.
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