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Biomedical subjects

D A Howell

Publications and source records attributed to D A Howell.

At least 37 records · Page 2Linked to original sources
PubMed1991

Biliary patency imaging after endoscopic retrograde sphincterotomy with gallbladder in situ. Clinical impact of nonvisualization.

We prospectively performed nuclear biliary patency imaging (HIDA scanning) in 62 patients who had undergone endoscopic retrograde sphincterotomy for management of pancreaticobiliary disease with their gallbladders in situ. Elective cholecystectomy was not recommended because of advanced age, comorbidity, or absence of gallstones. All patients had patent cystic ducts at endoscopic retrograde cholangiopancreatography balloon cholangiography. Eighteen (29.1%) of 62 patients had nonvisualizing HIDA scans, and in 44 (70.9%) of 62 visualization was normal or delayed. Six cholecystectomies were required for colic (n = 1), acute cholecystitis (n = 4), and acute cholecystocholedochal fistula with cholangitis (n = 1). Among the patients with cholelithiasis and nonvisualization (n = 13), five (38.5%) required surgery, whereas only one (4.8%) of 21 patients with cholelithiasis and visualization required surgery. Nonvisualizing HIDA scans are frequent (30%) after endoscopic retrograde sphincterotomy and have no clinical relevance in patients without cholelithiasis but predict the need for cholecystectomy within 16 months in 38.5% of patients with cholelithiasis.

Aged↗
PubMed1987

Immunological conservation of phycobilisome rod linker polypeptides.

Monospecific polyclonal antibodies raised against the phycobilisome rod linker polypeptides of Nostoc sp. were used to assess structural similarities among phycobilisome linker proteins from diverse, phycobilisome-containing organisms. While a remarkable conservation of antigenic determinants was demonstrated for two of these rod linker proteins, the third linker polypeptide appeared to be conserved only among closely related species.

Journal Article↗
PubMed1986

The immunologically conserved phycobilisome-thylakoid linker polypeptide.

We have isolated phycobilisomes from two classes of red algae, several subdivisions of the cyanobacteria, and the cyanelles of Cyanophora paradoxa. In addition to the major light harvesting biliproteins, these phycobilisomes also contain several other polypeptides, the largest of which ranges from 75 to 120 kilodaltons in the different species surveyed. This protein, previously isolated and characterized from three species, was shown to be the final emitter of excitation energy in phycobilisomes and is also thought to be involved in the attachment of the phycobilisomes to the thylakoid membrane. We have obtained polyclonal antibodies to the 95 kilodalton polypeptide isolated from phycobilisomes of the cyanobacterium, Nostoc sp. This protein shares no common antigenic determinants with either the alpha or beta subunits of allophycocyanin, or any of the other biliproteins, as determined by the sensitive Western immunoblotting technique. However, this antiserum cross-reacts with the highest molecular weight polypeptide of all the rhodophytan and cyanobacterial phycobilisomes tested. That these proteins are immunologically related, but are unrelated to other biliproteins, is reminiscent of previous immunological studies of biliproteins which showed that while the three major spectroscopically distinct classes of biliproteins (phycoerythrin, phycocyanin, and allophycocyanin) shared no common antigenic determinants, there was a strong antigenic determinant to specific biliprotein classes which crossed taxonomic divisions.

Journal Article↗
PubMed1983

Role of the Colorless Polypeptides in Phycobilisome Assembly in Nostoc sp.

We have identified the function of the ;extra' polypeptides involved in phycobilisome assembly in Nostoc sp. These phycobilisomes, as those of other cyanobacteria, are composed of an allophycocyanin core, phycoerythrin- and phycocyanin-containing rods, and five additional polypeptides of 95, 34.5, 34, 32, and 29 kilodaltons. The 95 kilodalton polypeptide anchors the phycobilisome to the thylakoid membrane (Rusckowski, Zilinskas 1982 Plant Physiol 70: 1055-1059); the 29 kilodalton polypeptide attaches the phycoerythrin- and phycocyanin-containing rods to the allophycocyanin core (Glick, Zilinskas 1982 Plant Physiol 69: 991-997). Two populations of rods can exist simultaneously or separately in phycobilisomes, depending upon illumination conditions. In white light, only one type of rod with phycoerythrin and phycocyanin in a 2:1 molar ratio is synthesized. Associated with this rod are the 29, 32, and 34 kilodalton colorless polypeptides; the 32 kilodalton polypeptide links the two phycoerythrin hexamers, and the 34 kilodalton polypeptide attaches a phycoerythrin hexamer to a phycocyanin hexamer. The second rod, containing predominantly phycocyanin, and the 34.5 and 29 kilodalton polypeptides, is synthesized by redlight-adapted cells; the 34.5 kilodalton polypeptide links two phycocyanin hexamers. These assignments are based on isolation of rods, dissociation of these rods into their component biliproteins, and analysis of colorless polypeptide composition, followed by investigation of complexes formed or not formed upon their recombination.

Journal Article↗
PubMed1981

Hypercalcemia complicating small-cell carcinoma.

Hypercalcemia is a common paraneoplastic syndrome complicating some varieties of lung cancer. It has rarely been reported with small-cell carcinoma of the lung. Seven cases of hypercalcemia complicating small-cell carcinoma of the lung are described; clinical features indicate that significant bone or bone marrow involvement is present in all cases. Parathormone assays were found to be generally in the normal range, though inappropriate for the levels of hypercalcemia.

Adult↗
PubMed1981

Intrahepatic hematoma after aspiration liver biopsy. A prospective randomized trial using two different needles.

The purpose of this study was twofold: (1) to determine the incidence of intrahepatic hematoma after liver biopsy by the aspiration technique and (2) to compare the incidence of hematoma after biopsy with a needle of 1.6 mm vs 1.9 mm OD. Fifty-one patients were randomly assigned to be biopsied with the smaller needle and 46 with the larger. Hematomas, diagnosed by development of characteristic transient defects on liver scans done shortly after biopsy, occurred in two (4%) of those biopsied with the smaller needle and in none of those biopsied with the larger. This difference is not statistically significant. Neither patient who developed a hematoma had changes in vital signs, CBC, or serum alkaline phosphatase. One had a fivefold rise in SGOT; n the other, the SGOT remained normal. If these results are considered with those of other prospective trials of similar design, the overall incidence of intrahepatic hematoma after aspiration biopsy may be estimated to be 2.3% when needles of 1.6-2.0 mm (OD) are used. Many of these go undetected because, justifiably, scans are not routinely done shortly after biopsies.

Biopsy, Needle↗
PubMed1980

Pulmonary hypertension as a presentation of hepatocarcinoma. Report of a case and brief review of the literature.

A case, unique in the literature, is reported in which a primary carcinoma of the liver presented a right-sided heart failure and pulmonary hypertension. The diagnosis of hepatocarcinoma was established by needle biopsy of the liver. Later, postmortem examination demonstrated that the pulmonary arterial tree was severely compromised by multiple tumor microemboli, despite the persistent lack of characteristic roentgenographic abnormality in our patient. In reviewing the literature, we found rare cases of occult renal cell carcinoma, choriocarcinoma and one of occult hepatocarcinoma, which presented as pulmonary embolism. These were diagnosed by pulmonary embolectomy, human chorionic gonadotrophin levels or autopsy, respectively. In another small group of reported cases of known carcinoma (gastric, breast, colonic) the patients had a clinical picture of "idiopathic" pulmonary hypertension or of pulmonary hypertension with pulmonary metastases. Pulmonary hypertension in these cases resulted from carcinomatous lymphangitis and/or tumor microembolization, as in our case. We report this case to emphasize the necessity of including occult carcinoma in the differential diagnosis of pulmonary hypertension and right ventricular failure.

Carcinoma, Hepatocellular↗
PubMed1979

Olfactory mucosa in herpes simplex encephalitis.

The olfactory mucosa was examined in three patients dying from herpes simplex encephalitis. It showed changes attributed to infection by the herpes simplex virus. It is suggested that in some patients encephalitis may be a complication of infection of the olfactory mucosa.

Adult↗
PubMed1979

Spinal internuncial neurones in progressive encephalomyelitis with rigidity.

The clinical and pathological features of a fourth patient with progressive encephalomyelitis with rigidity are reported and compared with those previously described. It is suggested that the muscular rigidity, abnormal postures, painful muscular spasms, and myoclonus are a product of excessive and abnormal discharges of alpha motor neurones caused by their release from control by spinal internuncial neurones. A count of neuronal perikarya in the ventral horns confirmed that the disease selectively destroyed small and medium sized neurones, most of which were spinal internuncial neurones. Experimental, clinical, and pathological evidence concerning spinal internuncial neurones is reviewed and found to conform to this theory. The pathogenesis of opsoclonus may be similar.

Astrocytes↗