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Biomedical subjects

M Post

Publications and source records attributed to M Post.

At least 145 records · Page 8Linked to original sources
PubMed1990

Constrained arthroplasty: its use and misuse.

Constrained arthroplasty is occasionally needed to salvage a destroyed glenohumeral joint when the rotator cuff is nonfunctioning and when an unconstrained prosthesis will not suffice. There is a high failure rate because of the severe forces between such a device and the contiguous bone. Accordingly, it is essential to know the limitations of constrained arthroplasty and when it should be avoided. For example, when the bone of the glenoid vault is highly demineralized or deficient or if there is a history of seizure disorder or alcoholism, use of such a device is contraindicated. Postoperatively, excessive force and extremes of motion should also be avoided during the rehabilitation program to avoid bone fracture or dislocation of the prosthesis. Various complications have been observed with constrained arthroplasty, including dislocation, bone fracture, pullout of the glenoid, infection, radial nerve injury after extrusion of bone cement through the humeral cortex when the cement has been pressurized, and screw breakage in a relative small number of cases after metal fatigue and loosening of the glenoid component. When the glenoid component has pulled away from the glenoid vault, it may be necessary to remove this component; the humeral head may be fitted with a bipolar 40- to 44-mm acetabular component, thereby allowing at least preservation, if not the active function of the shoulder contour.

Biomechanical Phenomena↗
PubMed1990

Complications of rotator cuff surgery.

It is essential to understand shoulder anatomy and the pathology and extent of a rotator cuff tear before an effective repair can be achieved. Most surgical-repair failures can be avoided by: (1) achieving adequate healing of the deltoid that has been detached from the acromion, (2) not excising too much of the acromion, (3) correctly repairing the rotator cuff, including intimal tears, and (4) carefully preserving the nerve supply to important shoulder girdle muscles. Nevertheless, if a complication arises, it must be correctly managed in order to salvage shoulder function.

Humans↗
PubMed1990

A comparative study of clinical muscle testing and Cybex evaluation after shoulder operations.

One hundred consecutive patients treated with shoulder surgery were studied to determine their functional recovery. Their average age was 47.3 years, and the average follow-up period was ten months. Clinical grading of muscle strength was compared pre- and postoperatively with objective testing using the Cybex II Isokinetic System, with subjective functional assessment by dictation, and with the ability of the patient to return to work. The clinical grade of muscle strength increased postoperatively by approximately one-half of a grade in both forward flexion and external rotation. However, various Cybex parameters did not significantly improve. The postoperative values were significantly less for the operated side than for the uninvolved side. Only weak statistical correlations were found between the clinical muscle grading and objective Cybex evaluation. Pain relief was obtained in 87% of the patients. Eighty-six percent of the patients returned to work, although 43% returned to light duty only. Thirty-two percent of patients reported full recovery, while 58% had decreased but satisfactory function. The study showed that although the clinical assessment of muscle strength improved early after shoulder surgery, the clinical grading of muscle power did not correlate well with objective parameters of strength, endurance, ability to work, or functional assessment. Strength did not recover to the level of the uninvolved opposite shoulder. Endurance, which is not measured by clinical grading, may decrease. Longer follow-up and rehabilitation periods are required to optimize results.

Adolescent↗
PubMed1989

Rotator cuff sonography: a reassessment.

This study is both a retrospective and prospective evaluation of the clinical usefulness of shoulder sonography. Ninety-eight patients suspected of having rotator cuff tears underwent sonography of both shoulders. Sixty-two patients underwent double-contrast arthrography performed on the same day as sonography, and 38 patients underwent surgery after sonography. A comparison of the results from ultrasound and arthrography, using published diagnostic criteria, demonstrated a sensitivity of 75% and a specificity of 43% for detection of a rotator cuff tear. In this study, use of more restricted criteria, a subset of the published criteria, yielded a sensitivity of 68% and a specificity of 90%. A comparison of sonography with surgery, using this study's criteria, demonstrated a sensitivity of 57% and a specificity of 76%. This report shows that shoulder sonography is less reliable than previously reported and appears to have a very limited role in the evaluation of rotator cuff injuries.

Adult↗
PubMed1989

Fibroblast-pneumonocyte factor.

Fibroblast-pneumonocyte factor (FPF) is an organ-specific differentiation factor produced, under glucocorticoid regulation, by the fetal lung fibroblast, which in turn enhances the differentiation of the alveolar type II cell with respect to surfactant production. In this article we review the appearance of the type II cell phenotype during fetal life and the action of FPF to time full acquisition of this phenotype. Evidence supporting a physiological role for this factor is reviewed as are details of its production by the fetal lung fibroblast and action on the type II cell. Finally we summarize possible future clinical advantages of using such a material to regulate lung maturation compared with currently used maternal glucocorticoid therapy. These include a more rapid effect and bypassing the inhibition of glucocorticoid action seen in male fetuses and in infants of diabetic mothers.

Animals↗
PubMed1989

Current concepts in the treatment of fractures of the clavicle.

Clavicle fracture is a common injury in all age groups. Injuries can be classified into groups. Group I includes fractures of the middle one third, the most frequent site. Group II fractures account for 10% of fractures of the clavicle and involve the clavicle lateral to the coracoclavicular ligament and are caused by direct violence. These injuries are divided into two subsets. Group II Type I fractures occur lateral to the coracoclavicular ligaments and are stable. Group II Type II fractures occur just medial to the coracoclavicular ligaments and are unstable. These latter injuries require stabilization. Group III fractures are uncommon and involve the medial end of the clavicle and are rarely caused by direct violence. Most fractures of the clavicle can be treated closed with excellent results. Open treatment is only occasionally indicated and then only under certain stringent conditions. Most complications occur with open treatment and include nonunion and infection. Neurovascular complications are uncommon but not unusual. Although reasonable shoulder function is compatible with surgical resection of the clavicle, it cannot be done with impunity.

Adolescent↗
PubMed1989

Primary tendinitis of the long head of the biceps.

Seventeen patients with chronic painful shoulders who showed evidence of isolated bicipital tendinitis involving only the extracapsular, intertubercular portion of the long head of the biceps were chosen for surgical treatment when conservative treatment failed. The patients were thought to have primary bicipital tendinitis. The latter condition is secondary to other shoulder pathologies. Thirteen patients had tenodeses and four patients had transfer of the long head of the biceps to the origin of the conjoined tendon. Overall, excellent and good results were noted in 94% of both groups of patients when the long head of the biceps was tenodesed or transferred. Whether or not the long head of the biceps is a significant depressor of the humeral head requires further investigation.

Adult↗
PubMed1988

Histochemical and immunocytochemical identification of alveolar type II epithelial cells isolated from fetal rat lung.

Primary cultures of epithelial cells isolated from organotypic cultures of fetal (Days 18 through 22) rat lung have been characterized by histochemical and immunocytochemical parameters. Immunocytologic analysis with monoclonal antibodies to cytokeratins and with those to adult type II cells (JBR-1) demonstrated that the cell cultures were composed almost entirely of epithelial type II cells. Additional evidence that the cultures had the type II phenotype was obtained by Maclura pomifera lectin binding studies and by positive immunocytochemical demonstration of surfactant apoproteins. Comparison of cell cultures established from fetal lung at the early canalicular and saccular stages of rat lung development revealed that early fetal type II cells (Day 19) contained much glycogen and few lamellar bodies. The reverse was observed in type II cells isolated from fetal lungs at 21 days of gestation. Immunohistochemically determined surfactant apoproteins showed a similar developmental pattern to lamellar bodies. The cell cultures exhibited alkaline phosphatase activity, but this did not increase with development. Administration of dexamethasone to pregnant rats at 19 days gestation resulted in a significant loss of glycogen from fetal type II cells isolated 24 h later. This decrease in glycogen content was accompanied by an increase in the number of cells containing lamellar bodies. These findings indicate that freshly isolated fetal type II cells retain the morphologic features of the type II cells in vivo and provide a good system for the study of biochemical events occurring in these cells during specific stages of lung development.

Animals↗
PubMed1987

Maternal administration of dexamethasone stimulates choline-phosphate cytidylyltransferase in fetal type II cells.

Administration of dexamethasone to pregnant rats at 19 days gestation increased phosphatidylcholine synthesis (45%) from radioactive choline in type II cells. This enhanced synthesis of phosphatidylcholine was accompanied by an increased conversion of choline phosphate into CDP-choline. Similar results were obtained by incubating organotypic cultures of 19-day-fetal rat lung with cortisol. The increased conversion of choline phosphate into CDP-choline correlated with an enhanced choline-phosphate cytidylyltransferase activity (31% after dexamethasone treatment; 47% after cortisol exposure) in the cell homogenates. A similar increase (26% after dexamethasone treatment; 39% after cortisol exposure) was found in the microsomal-associated enzyme. No differences in cytosolic enzyme activity were observed. The specific activity of the microsomal enzyme was 3-4 times that of the cytosolic enzyme. Most of the enzyme activity was located in the microsomal fraction (58-65%). The treatments had no effect on the total amount of enzyme recovered from the cell homogenates. These results, taken collectively, are interpreted to indicate that the active form of cytidylyltransferase in type II cells is the membrane-bound enzyme and that cytidylyltransferase activation in type II cells from fetal rat lung after maternal glucocorticoid administration occurs by binding of inactive cytosolic enzyme to endoplasmic reticulum.

Animals↗
PubMed1987

Temporal linkage of glycogen and saturated phosphatidylcholine in fetal lung type II cells.

The developmental profiles of glycogen and surfactant-associated saturated phosphatidylcholine were investigated in type II cells isolated from fetal rat lung. Incorporation of radiolabeled glucose into glycogen and type II cell unlabeled glycogen content decreased as a function of gestational age. Conversely, an increase was noted in radioactive choline incorporation into saturated phosphatidylcholine and in the content of unlabeled saturated phosphatidylcholine as a function of gestational age. Type II cells from days 19 and 21 of gestation were also studied by electron microscopy. Temporal relationships similar to those noted biochemically were observed by morphometric analysis. A decrease in glycogen content and an increase in lamellar bodies (the storage organelles for the pulmonary surfactant) were noted as gestation progressed. These studies biochemically and morphologically demonstrate a temporal relationship between glycogen degradation and saturated phosphatidylcholine synthesis in type II cells isolated from fetal rat lung. These findings provide further support for the use of such type II cell preparations for studies of development at the cellular level.

Animals↗
PubMed1987

Characterization of proteoglycans synthesized by fetal rat lung type II pneumonocytes in vitro and the effects of cortisol.

The synthesis of proteoglycans by primary cultures of 19-day gestation fetal rat lung Type II pneumonocytes was studied. The cells were grown in the presence of [3H]-glucosamine and/or [35S]-Na2SO4 and the radioactive label incorporated into proteoglycans was analyzed. Proteoglycans of high molecular weight (approximately 200 Kd) were isolated by gel permeation chromatography and contained both [3H] and [35S]. The glycosaminoglycan composition of the proteoglycans was determined by electrophoresis and autoradiography. The medium contained 65-80% of the labeled proteoglycans and was enriched for hyaluronate, with lesser amounts of the sulfated glycosaminoglycans (dermatan sulfate greater than heparan sulfate greater than chondroitin sulfate). The cell layers retained 20-35% of the labeled proteoglycans and was enriched for heparan sulfate, with lesser amounts of chondroitan sulfate greater than dermatan sulfate greater than hyaluronate. The synthesis of proteoglycans was time-dependent and was stimulated by increasing concentrations of fetal bovine serum. Cortisol inhibited proteoglycan synthesis, apparently by decreasing the availability of proteoglycan core-protein.

Animals↗
PubMed1987

Constrained arthroplasty of the shoulder.

Constrained replacement, like all prosthetic replacements, is constantly undergoing change and will improve as the current state of the art changes. It is not a standard, usual operation like unconstrained arthroplasty, and it should be reserved for the patient who requires arthroplasty and does not have a functional rotator cuff mechanism. If, in addition, the acromial fulcrum and loss of deltoid is present, then there is a greater reason for constrained replacement; it is a salvage procedure that is not as durable as the unconstrained device. Constrained arthroplasty has much merit if the risks and possible complications are well understood; however, pain relief and improved function will be lost if the device fails. The dislocation feature of the MRTS is desirable in order to minimize the risk of scapular fracture. Its disadvantage is that, with this complication, open operation is needed to reduce the assembly and insert new polyethylene components. The method of surface mounting of the metal glenoid component without removing the glenoid subchondral plate or cancellous bone of the vault is believed to lessen the risk of glenoid component loosening or pull-out. Finally, active function always depends upon residual deltoid muscle power. Thus, a poor or absent deltoid will only permit passive motion.

Humans↗
PubMed1987

Suprascapular nerve entrapment. Diagnosis and treatment.

Nine patients were found to have suprascapular nerve entrapment confirmed by electromyographic studies after the diagnosis was suspected. Eight patients who had a surgical release of the suprascapular ligament had good and excellent results. Except in rare cases, a positive electromyogram (EMG) including a delayed nerve conduction (using a coaxial needle) is necessary confirming evidence of the need for surgical treatment. The recommended surgical technique involves detaching the trapezius muscle from the spine of the scapula and opening the space overlying the suprascapular ligament. The trapezius is retracted cephalad while the supraspinatus is retracted caudad. This exposure avoids injury to the spinal accessory nerve and promotes a rapid rehabilitation. Suprascapular nerve entrapment should be suspected and included in the differential diagnosis of ill-defined shoulder pain.

Adult↗
PubMed1986

The cellular mechanism of glucocorticoid acceleration of fetal lung maturation. Fibroblast-pneumonocyte factor stimulates choline-phosphate cytidylyltransferase activity.

The cellular mechanism by which glucocorticoids stimulate phosphatidylcholine biosynthesis has been studied in the fetal rat lung in vivo and in cultured fetal rat lung cells of varying levels of complexity. Administration of dexamethasone to pregnant rats at 18 days gestation resulted in a significant increase in saturated phosphatidylcholine content in fetal lung 24 h after injection. Dexamethasone administration increased the activity of fetal lung choline-phosphate cytidylyltransferase by 34%. It had no effect on the activities of fetal lung choline kinase and choline phosphotransferase. Exposure of fetal lung type II cells in organotypic cultures (which contain both type II cells and fibroblasts) to cortisol resulted in a 1.6-fold increase in the incorporation of [Me-3H]choline into saturated phosphatidylcholine. The activities of the enzymes in the choline pathway for the de novo biosynthesis of phosphatidylcholine were not significantly altered except for a 105% increase in choline-phosphate cytidylyltransferase activity. Treatment of monolayer cultures of fetal type II cells with cortisol-conditioned medium from fetal lung fibroblasts resulted in a 1.5-fold increase in saturated phosphatidylcholine production. This effect correlated with a doubling of choline-phosphate cytidylyltransferase activity. Additional evidence that this stimulatory action is mediated by fibroblast-pneumonocyte factor, produced by fetal lung fibroblasts in response to cortisol, was obtained. The factor was partially purified from cortisol-conditioned medium of fetal lung fibroblasts by gel filtration and affinity chromatography. Based on biological activity, a 3000-fold purification was obtained. Stimulation of saturated phosphatidylcholine synthesis in type II cells by fibroblast-pneumonocyte factor was maximal within 60 min of incubation. Pulse-chase experiments indicated that the stimulatory effect was correlated with an increased conversion of choline phosphate into CDP choline. Moreover, the enhanced phosphatidylcholine formation by fetal type II cells in response to fibroblast-pneumonocyte factor was accompanied by decreased levels of cellular choline phosphate. These findings further support the concept that glucocorticoid action on surfactant-associated phosphatidylcholine synthesis occurs ultimately at the level of the alveolar type II cell and involves fibroblast-pneumonocyte factor which stimulates the activity of choline-phosphate cytidylyltransferase.

Animals↗
PubMed1986

Reciprocal autocrine and paracrine regulation of growth of mesenchymal and alveolar epithelial cells from fetal lung.

The regulation of DNA synthesis in 19 day rat fetal lung epithelial (alveolar type II) and mesenchymal (fibroblast) cells by protein growth factors has been studied. In each case a single growth factor is capable of stimulating 3H-thymidine incorporation into DNA: platelet-derived growth factor in the case of the alveolar type II cell and epidermal growth factor in the case of the fetal lung fibroblast. We hypothesize that these results indicate that the type II cell endogenously produces progression activities (i.e., epidermal growth factor-like and somatomedin-like activity) while the fibroblast produces competence (i.e., platelet-derived growth factor-like) and progression (i.e., somatomedin-like activity). The latter is in keeping with previous observations with skin fibroblasts. To test the above hypothesis, the effect of fetal lung fibroblast-derived conditioned media upon the growth of fetal alveolar type II cells has been determined. The results indicate that, indeed, such media contain competence activity for this cell type. The mitogenic activity was further characterized as heat-sensitive, trypsin-sensitive, and has an apparent molecular weight of 30,000 Daltons. It is not synthesized by 19 day fetal liver, kidney or skin fibroblasts and its synthesis is higher in lung fibroblasts isolated from 19 day fetuses as compared to those isolated on day 16 or day 22.

Animals↗