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Biomedical subjects

A Cooper

Publications and source records attributed to A Cooper.

At least 289 records · Page 16Linked to original sources
PubMed1987

External silo reduction of the unruptured giant omphalocele.

Construction of an external silo dressing over the intact omphalocele membrane allows complete reduction of the giant omphalocele with enlargement of the abdominal cavity before surgical intervention, so that primary closure of the abdominal wall can be achieved. Three infants with giant omphalocele containing a central liver were successfully managed by this technique avoiding the complications associated with operative silo placement or simple membrane painting.

Bandages↗
PubMed1987

Microdiverticulitis: a rare but distinct cause of small bowel obstruction in early infancy.

During a 20-year period, eight term infants admitted to a large children's hospital for treatment of dehydration associated with diarrhea (6) and vomiting (2), and who ranged in age from 10 to 60 days at onset of symptoms and 18 to 75 days at presentation, developed distal small bowel obstruction following apparently successful rehydration. With the exception of a single infant who was dead on arrival, and another whose obstruction went unrecognized, all infants came to operation shortly after obstruction was confirmed. In each case, a severely inflamed area of distal ileum (7) or proximal colon (1) was found at autopsy (2) or operation (6) to be the cause; perforation was present in four of the cases. Resection of the diseased segments of intestine, and primary anastomosis, were performed in all six operated cases; reoperation was required in four of the six for leaks (3) and adhesions (1). All but two survived. Pathologically, the resected intestinal segments showed a unique pattern of injury: numerous punctate ulcers were apparent, which undermined the muscularis mucosae, without evidence of necrosis. Regenerating epithelium extended through these defects, resulting in the presence of glandular invaginations, which were surrounded by a brisk inflammatory response: hence the term "microdiverticulitis." We believe this lesion represents a beginning or furtive attempt at repair of severely inflamed, but viable intestine, and that it is a rare but true cause of small bowel obstruction in early infancy, separate and distinct from necrotizing enterocolitis.

Diverticulitis↗
PubMed1987

Quantum efficiencies of the reversible photoreaction of octopus rhodopsin.

The classic method of photometric curves for photosensitivity determination has been extended to the case of photoreversible reactions and applied to the octopus rhodopsin --> acid metarhodopsin photoreaction. In such cases, measurements at one irradiation wavelength yield the sum of the photosensitivities of the forward and reverse processes. However, by using different irradiation wavelengths, together with appropriate molar extinction coefficients, the quantum efficiencies for both reactions may be resolved. For detergent-solubilized octopus rhodopsin at room temperature, pH 7, the quantum yields are found to be 0.69 (+/- 0.03) for rhodopsin --> metarhodopsin, in line with values observed in a range of vertebrate visual pigments, and 0.43 (+/- 0.02) for the reverse photoregeneration process. The similarities in overall photosensitivities of the forward and reverse reactions in the visible region are consistent with a significant physiological role for photoreversal in the cephalopod visual cycle.

Animals↗
PubMed1987

Bone marrow transplantation in the treatment of alpha-mannosidosis.

Bone marrow transplantation was performed in a patient with alpha-mannosidosis. To our knowledge this is the first time such treatment has been attempted. The patient died 18 weeks after successful grafting and specimens of tissues were obtained at necropsy. Alpha-mannosidase activity in spleen and liver was just below normal (spleen 102 mumol/g/hour, control 113-330; liver 29 mumol/g/hour, control 30-131). Splenic alpha-mannosidase activity was indistinguishable from the control enzyme with respect to the Michaelis constant, heat stability, and inhibition by cobalt ions, as was 86% of the liver enzyme. In brain tissue alpha-mannosidase activity was 7% of controls, and less than one third had the properties of the normal enzyme. Oligosaccharides were present only in small amounts in liver and spleen, whereas they were greatly increased in brain tissue. Electron microscopic pictures of liver and spleen tissue showed normal morphology, but brain tissue showed definite vacuolation. These findings suggest that transplantation reversed the somatic changes of alpha-mannosidosis but did not affect lysosomal storage within brain tissue. It is concluded that marrow transplantation may not be a suitable treatment for alpha-mannosidosis.

Bone Marrow Transplantation↗
PubMed1986

Photoenergetics of octopus rhodopsin. Convergent evolution of biological photon counters?

The enthalpy changes associated with each of the major steps in the photoconversion of octopus rhodopsin have been measured by direct photocalorimetry. Formation of the primary photoproduct (bathorhodopsin) involves energy uptake of about 130 kJ/mol, corresponding to storage of over 50% of the exciting photon energy, and is comparable to the energy storage previously observed in bovine rhodopsin. Subsequent intermediates involve the step-wise dissipation of this energy to give the physiological end-product (acid metarhodopsin) at a level only slightly above the parent rhodopsin. No significant differences in energetics are observed between rhodopsin in microvilli membrane suspensions or detergent dispersions. Use of different buffer systems in the calorimetric experiments shows that conversion of rhodopsin to acid metarhodopsin involves no light-induced protonation change, whereas alkali metarhodopsin photoproduction occurs with the release of one proton per molecule and an additional enthalpy increase of about 50 kJ/mol. Van't Hoff analysis of the effect of temperature on the reversible metarhodopsin equilibrium gives an enthalpy for the acid----alkali transition consistent with this calorimetric result, and the proton release is confirmed by direct observation of light-induced pH changes. Acid-base titration of metarhodopsin yields an apparent pK of 9.5 for this transition, though the pH profile deviates slightly from ideal titration behaviour. We suggest that a high energy primary photoproduct is an obligatory feature of efficient biological photo-detectors, as opposed to photon energy transducers, and that the similarity at this stage between cephalopod and vertebrate rhodopsins represents either convergent evolution at the molecular level or strong conservation of a crucial functional characteristic.

Animals↗
PubMed1986

Primary hyperparathyroidism in infancy.

Primary hyperparathyroidism in the neonate is a rare and often fatal disorder. These infants typically display severe hypercalcemia, respiratory distress, muscular hypotonia, and skeletal demineralization. They are usually diagnosed within the first three months of life and have hyperplasia of the four parathyroid glands. Twenty-nine infants with primary hyperparathyroidism are reported in the literature. Mortality is 87.5% in medically managed patients and 24% in surgically managed patients. Surgical management has not been satisfactory, in that recurrent hypercalcemia has been encountered in most patients undergoing subtotal parathyroidectomy, and total parathyroidectomy has resulted in the need for lifelong calcium and vitamin D supplementation. We have recently cared for a term newborn female in whom the diagnosis of primary hyperparathyroidism was made clinically on the second day of life, and later was confirmed biochemically. The baby underwent neck exploration on the 11th day of life and was successfully treated with total parathyroidectomy and parathyroid autotransplantation. Although initially rendered eucalcemic, the infant subsequently developed recurrent hypercalcemia requiring the removal of some of the autograft. Currently, the child is more than 2 years following surgery, growing well, and off all medication. The world literature is reviewed in this report of one of the first and the youngest infants, to our knowledge, to undergo parathyroid autotransplantation. In view of its success in avoiding the complication of repeated neck exploration for recurrent hyperparathyroidism or the creation of permanent hypoparathyroidism, we recommend this surgical approach for the rare neonate with primary hyperparathyroidism.

Biopsy↗
PubMed1986

Management of vascular complications of bacterial endocarditis.

Peripheral arterial emboli that result from bacterial endocarditis may be silent or catastrophic. Cardiac surgical intervention may prevent embolism, but the guidelines for timing of intervention are unclear. An accepted approach is to intervene only if two episodes of peripheral embolism occur. Our recent experience suggests a more refined approach is in order. Eight children with active bacterial endocarditis have been treated with embolic complications. One patient with abdominal pain and GI bleeding was treated with heparin for multiple peripheral mesenteric emboli. Four patients had femoral embolectomies, one twice. Three patients developed embolomycotic aneurysms of the aorta in two cases and the common iliac in one; all were ruptured and two survived with staged reconstruction in one and extra-anatomic bypass in the other. Staph aureus and Strep viridans were the organisms involved most often. A review of the details of care in these patients leads to the following conclusions: angiographic survey reveals that most patients have multiple emboli; early embolectomy may prevent formation of infected aneurysms; Staph aureus infected patients are at risk for development of infected aneurysms; patients with large floppy vegetations in the left heart on echocardiography are at high risk for embolism; and 2 to 3 weeks from onset of endocarditis is the peak time for embolic risk.

Adolescent↗
PubMed1985

Resolution of intractable cholestasis associated with total parenteral nutrition following biliary irrigation.

Although the protracted use of total parenteral nutrition (TPN) in infants is known to predispose to cholestasis, which in certain instances may not be reversible, failure to understand the pathogenesis of this condition has hindered the development of an effective medical treatment. That surgical treatment may reverse this process in selected patients is the subject of the present report. Two premature infants and one term infant, with short bowel syndrome acquired in infancy, developed conjugated hyperbilirubinemia following institution of balanced TPN. Infectious and metabolic etiologies for the jaundice were ruled out. No excretion of 99mTc-labeled DISIDA from the biliary tree was demonstrable 24 hours following injection by nuclear scintigraphy, despite the absence of extrahepatic biliary obstruction by abdominal sonography. When all conventional medical methods of managing the problem failed, exploration was performed. Intraoperative cholangiography showed normal intrahepatic and extrahepatic biliary ducts in each instance. Irrigation of the biliary tree with normal saline solution was then performed. In all cases, liver biopsies were obtained that were consistent with TPN-associated cholestasis and in all cases, jaundice resolved promptly following operation. We conclude that intractable cholestasis associated with TPN, regardless of its etiology, is a functional abnormality of biliary excretion that may respond in selected patients to irrigation of the biliary tree with radiographic dye and/or normal saline solution.

Biliary Tract↗
PubMed1985

Spatial location judgments as a function of intention to learn, and mood state: an evaluation of an alleged automatic encoding operation.

An assessment of the Hasher and Zacks (1979) conceptualization of the automatic nature of the acquisition of spatial location information was made in the context of manipulations of subjects' intention to learn and mood state. The Velten (1968) mood induction procedure was used to establish depressed and nondepressed subjects. Half of each group was then presented with a matrix of geometric forms under instructions to learn the location of the forms (intentional) or to evaluate the pleasantness of the array (incidental). Subsequent tests of spatial location performance found no differences as a function of subjects' mood state, but did find a strong effect for instructional condition. The superior performance of the intentional subjects raises questions about the automatic nature of the encoding of spatial location.

Adult↗
PubMed1984

Changes in guinea pig plasma cyclic nucleotide levels during the development of a transplantable leukemia.

Plasma levels of cyclic AMP and cyclic GMP were determined in 35 guinea pigs for up to 9 days following subcutaneous passage of L2C leukemia cells. Twenty guinea pigs into which normal syngeneic guinea pig thymocytes were passaged served as controls. Cyclic AMP levels in plasma showed little change and were only elevated significantly in test animals on day 9 after passage. In contrast cyclic GMP levels reached a maximum on day 5 after passage of leukemia cells with two to threefold rises over day 1 levels. Increases in leukocyte counts were not observed until day 7 in test animals. Of the other tumour growth indices which were examined, the axillary (draining) node index gave the earliest indication of cell proliferation, with significant elevations on day 3 after passage. The authors conclude that plasma cyclic GMP increases precede increases in white cell counts by at least 2 days, and may reflect an early increase in axillary node growth.

Animals↗
PubMed1984

Correlations between clonogenicity and prognostic factors in human breast cancer.

The pursuit of more effective systemic treatments in breast cancer has been limited by a failure to maintain or grow tumour cells in vitro. This study reports our experience in obtaining clonogenic growth in 54 primary breast cancers obtained at mastectomy. Of 47 assays free of infection, clonogenic growth was achieved in 22 (41 per cent). Only 5 of 23 oestrogen receptor positive tumours grew compared to 14 of 21 oestrogen receptor negative tumours chi 2 = 9.03; P less than 0.01). None of the 5 cytosolic receptor positive tumours contained a nuclear receptor for oestrogen. Growth was not related to tumour stage, menopausal status, age or histological grade. Receptor negative tumours had higher thymidine labelling indices, but these were no different to the tumours grown in the assay.

Breast Neoplasms↗
PubMed1984

Allostery without conformational change. A plausible model.

A general model is presented whereby ligand-induced changes in protein dynamics could produce allosteric communication between distinct binding sites, even in the absence of a macromolecular conformational change. Theoretical analysis, based on the statistical thermodynamics of ligand binding, shows that cooperative interaction free energies amounting to several kJ . mol-1 may be generated by this means. The effect arises out of the possible changes in frequencies and amplitudes of macromolecular thermal fluctuations in response to ligand attachment, and can involve all forms of dynamic behaviour, ranging from highly correlated, low-frequency normal mode vibrations to random local anharmonic motions of individual atoms or groups. Dynamic allostery of this form is primarily an entropy effect, and we derive approximate expressions which might allow the magnitude of the interaction in real systems to be calculated directly from experimental observations such as changes in normal mode frequencies and mean-square atomic displacements. Long-range influence of kinetic processes at different sites might also be mediated by a similar mechanism. We suggest that proteins and other biological macromolecules may have evolved to take functional advantage not only of mean conformational states but also of the inevitable thermal fluctuations about the mean.

Allosteric Regulation↗
PubMed1984

Taurine deficiency in the severe hepatic dysfunction complicating total parenteral nutrition.

The etiology of the severe hepatic dysfunction associated with total parenteral nutrition (TPN) remains unknown, but recent studies suggest that taurine deficiency may be associated with the development of cholestasis in experimental animals. That taurine deficiency might also play a role in the development of the severe hepatic dysfunction in human infants receiving TPN as their sole nutritional intake is the subject of the present report. Serial plasma aminograms were obtained from three children with severe hepatic dysfunction associated with TPN, in whom progressive disease led to death after 20, 13, and 14 months. All three children underwent massive intestinal resection for necrotizing enterocolitis, leaving 30, 44, and 17 cm of viable small bowel, respectively. Balanced TPN was given as 20 to 25 g/kg/d dextrose, 1.5 to 2.5 g/kg/d crystalline amino acids, and 2 to 3 g/kg/d fat emulsion; enteral feedings were attempted but were poorly tolerated. Mild cholestasis progressed to severe hepatic dysfunction manifested by hyperbilirubinemia, increased serum transaminases, hypoproteinemia, and abnormal coagulation profiles. Liver histology revealed extensive fibrosis, fatty replacement, and coarse cholestasis, necrosis not being prominent. Serial plasma aminograms revealed markedly elevated plasma levels of methionine (1353, 1168, and 113 nm/mL), low levels of 1/2 cystine (68.4, trace, and 17 nm/dL), and undetectable levels of taurine; plasma levels of branched-chain amino acids were normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗