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Biomedical subjects

J T Davis

Publications and source records attributed to J T Davis.

At least 19 recordsLinked to original sources
PubMed1992

Myxoid heart disease: an assessment of extravalvular cardiac pathology in severe mitral valve prolapse.

Because of the microscopic features of the affected leaflets in mitral valve prolapse (MVP), myxoid degeneration of the valve is a common pathologic designation applied to this condition. We undertook this study as a means of gaining an insight into the occurrence and prevalence of extravalvular cardiac alterations in hearts with severe MVP. Tissues of 24 hearts with severe myxomatous transformation of the mitral valve as the sole cardiac abnormality were examined. Eighteen of the 24 subjects with severe MVP died suddenly. Only two of these had pathologic evidence of severe mitral insufficiency. Twenty-four normal hearts served as controls. The two groups of hearts came from victims of homicide, suicide, accident, or natural death. Sections of the mitral valve, working myocardium, conduction system, and cardiac nerves and ganglia were studied by routine and special connective tissue and proteoglycan stains. Similar to the findings in severely affected mitral valves, prominent deposits of proteoglycans in neural and conduction tissue readily distinguished hearts with myxomatous valve changes from the control hearts. We conclude that the commonly recognized local derangement of valvular tissue in MVP is but one specific reflection of a more general myxomatous alteration in cardiac connective tissue.

Adolescent↗
PubMed1992

Synthesis and secretion of retinol-binding protein by cultured rat Sertoli cells.

We report here that retinol-binding protein (RBP) is synthesized and secreted by rat Sertoli cells in culture. This was demonstrated in four ways. First, transthyretin (TTR) bound to Sepharose 4B retained a labeled protein from media collected from Sertoli cells provided with 35S-methionine, under the same conditions as authentic RBP is bound. The protein was co-eluted with authentic RBP by pure water. Second, this same radioactive protein co-eluted with pure RBP upon gel filtration. Third, when subjected to SDS-PAGE, the protein again migrated with pure RBP, as shown by radioautography. Finally, Sertoli cells were incubated with 35S-cysteine and the conditioned medium was put over a TTR-Sepharose column to isolate the radioactive protein, as characterized above. Cysteine residues were oxidized to cysteic acid residues, and the protein was submitted for sequencing through the first ten residues. Radioactivity was located only in the fourth residue, where a cysteine residue is found in rat RBP. This indicates that RBP is secreted by the Sertoli cell and may serve as the carrier of retinol to the developing germ cells, which are known to be dependent upon vitamin A.

Amino Acid Sequence↗
PubMed1992

The application of the Screening Cerebral Assessment of Neppe (BROCAS SCAN) to a neuropsychiatric population.

Assessments of higher cortical functioning are often neglected in patients with possible coarse neurobehavioral psychiatric disease, such as dementia, stroke, or focal cerebral lesions. When performed, the short Folstein Mini-Mental State Exam (MMSE) is typically used. The authors' research on 45 neuropsychiatric patients compared the MMSE with a new 20-30-minute bedside examination, the Screening Cerebral Assessment of Neppe (BROCAS SCAN). This screens 10 areas: recall, recognition, orientation, organization of thought, concentration, calculation, agnosia, apraxia, speech, and sensory-motor-reflex phenomena. The BROCAS SCAN (total) correlated extremely well with neuropsychiatric prediction, MRI changes, and neuropsychological testing, and distinguished diagnoses, demonstrating construct and face validity. It also accounted for a larger proportion of variance than the MMSE in correlating with these parameters and was more sensitive in mildly cognitive impaired patients. The briefer first section of the BROCAS SCAN, the core SCAN, also showed statistically relevant relationships to age, diagnosis, MRI, and neuropsychiatric prediction.

Adolescent↗
PubMed1991

Prevalence of paediatric cardiac disease in rural Kenya.

A series of 31 patients referred for evaluation of paediatric cardiac disease in rural Kenya is reported. The prevalence of symptomatic rheumatic heart disease is unchanged from previous data in the literature which is well over a decade old. We can conclude that recent improvements in medical care in Kenya have not yet reached certain rural areas as far as rheumatic fever is concerned. In addition, a significant number of children presumed to have had no discernible heart disease at this evaluation, suggesting the need for critical re-evaluation of this population at intervals. Finally, cyanotic disease seems under-represented in the series, suggesting that infants with certain cyanotic lesions may have been selected out and hence not referred to us.

Child↗
PubMed1989

Congenital heart disease in Down's syndrome patients: a decade of surgical experience.

Patients with Down's syndrome represent a significant subset of patients with congenital heart disease. Fifty-five patients with Down's syndrome have undergone surgical treatment for congenital heart disease at our institution in the past decade. Twenty-six had atrioventricular canal, 11 had ventricular septal defect, 7 had secundum atrial septal defect, 7 had tetralogy of Fallot, 3 had primum atrial septal defect and 1 patient had double outlet right ventricle. The thirty day mortality following operative intervention was 16.4%. Mortality was highest for tetralogy of Fallot followed by atrioventricular canal and ventricular septal defect. Long term mortality for all lesions was 27.3% over our follow-up period which averaged 33 months. Thirty day mortality compared similarly to previous reports of surgically treated Down's syndrome patients. When compared to our patients without Down's syndrome, the Down's population did not exhibit an increased risk for surgical treatment of congenital heart disease.

Adolescent↗
PubMed1988

The cardiac apex and its superficial blood supply.

The cardiac apex was defined and 3 types were presented: the anatomical apex, the base of which was established at the incisura apicis cordis; the amplified anatomical apex, twice the volume of the preceding; and the geometric apex, the distal third of the ventricles. These types of cardiac apex were studied in connection with the superficial branches of the coronary arteries at their level. The investigation was conducted on 81 normal hearts (56 males and 25 females) of 60 Caucasian and 21 non-Caucasian individuals. The arteries were injected with colored gelatine mixed with a radiopaque substance. The number of branches decreased from the geometric (the largest type) to the anatomical apex (the smallest): 27 on the surface of the geometric apex, 14 on the surface of the amplified anatomical apex, and 7 on the surface of the anatomical apex. The sternocostal aspect had a higher number of superficial branches than the diaphragmatic aspect in all types of cardiac apex. Sexual differences were found in the incidence of the r posterior ventriculi sinistri intermedius on the amplified anatomical apex as it was more frequent in females than in males. In the geometric apex there were 3 branches also more frequent in females: r anterior ventriculi sinistri inferior, r posterior ventriculi sinistri lateralis I, and r posterior ventriculi sinistri lateralis IV.

Adolescent↗
PubMed1988

Vocal cord paralysis in premature infants undergoing ductal closure.

A series of 106 consecutive ductal closures in premature infants was reviewed to assess the incidence of left vocal cord paralysis. To our knowledge, this syndrome is described for the first time in premature infants. In our experience, it is a relatively benign complication that completely resolves clinically in several weeks. This complication occurred in 5.2% of patients closed by suture ligature and in none of those closed by a surgical clip. Although the series is too small for this difference to be statistically significant, we believe it strongly favors the use of the clip, with less dissection.

Ductus Arteriosus, Patent↗
PubMed1987

Biosynthetic thiolase from zoogloea ramigera. I. Preliminary characterization and analysis of proton transfer reaction.

The biosynthetic thiolase, from Zoogloea ramigera, involved in generation of acetoacetyl-CoA for poly-beta-hydroxybutyrate synthesis, has been prepared pure in quantity for initial structural characterization of this homotetrameric enzyme. Edman degradation provided the sequence of the NH2 terminal 25 residues and an active site cysteine-containing nonapeptide labeled on stoichiometric inactivation by iodoacetamide. Both sequences were used to align the encoding DNA sequence of the cloned gene as described in an accompanying paper. Synthetic analogs of acetoacetyl-S-CoA, modified in the CoA moiety, were prepared and tested, and acetoacetyl-S-pantetheine 11-pivalate 1 was shown to have a kcat/Km of 6.4 X 10(6) M-1 s-1, comparable to the kcat/Km of 2 X 10(7) M-1 s-1 for acetoacetyl-S-CoA. The pantetheine pivalate group facilitates nonaqueous synthetic manipulations and may be generally useful as a CoA replacement. We have also prepared the carba analog of 1, with CH2 replacing S, to yield a beta-diketone analog 10 of acetoacetyl-S-CoA and the corresponding methyl ketone analog 9 of acetyl-S-CoA. These analogs have been used to prove the ability of Z. ramigera thiolase to catalyze proton abstraction from the C-2 methyl group of the acetyl portion of substrate in a transition state separate from C-C bond formation. NMR studies in D2O show exchange only when condensation is possible. Further studies with [2-3H]acetyl-CoA show there is neither pre-equilibrium washout nor detectable kH/kT expressed in turnover and provide no evidence for a discrete acetyl-CoA C-2 carbanion or a nonconcerted reaction.

Acetyl Coenzyme A↗
PubMed1987

Biosynthetic thiolase from Zoogloea ramigera. II. Inactivation with haloacetyl CoA analogs.

The thiolase involved in biosynthesis of poly-beta-hydroxybutyrate in Zoogloea ramigera generates an acetyl-enzyme species during catalysis. Up to 0.86 [14C] acetyl eq/subunit of this homotetrameric enzyme is accumulated by acid precipitation in the presence of [14C]acetyl-CoA. Gel filtration of the same solutions produced only 7% acetyl-enzyme suggesting hydrolytic lability of the acetyl-enzyme during the 10-min isolation at 4 degrees C. In an effort to identify active site residues which may function as basic groups to deprotonate at C-2 of acetyl-CoA to generate the required nucleophilic equivalent in carbon-carbon bond formation, we have prepared and tested haloacetyl-thioesters, oxoesters, and amides in the panthetheine pivalate series (Davis, J. T., Moore, R. N., Imperiali, B., Pratt, A. J., Kobayashi, K., Masamune, S., Sinskey, A. J., and Walsh, C. T. (1987) J. Biol. Chem. 262, 82-89). The [14C]bromoacetyl-oxoester alkylatively inactivates thiolase irreversibly with stoichiometric incorporation of four labels/tetramer. Determination of amino acid composition of the radiolabeled tryptic peptide indicated trapping of Cys-89 (Peoples, O. P., Masamune, S., Walsh, C. T., and Sinskey, A. J. (1987) J. Biol. Chem. 262, 97-102), the same residue modified by iodoacetamide. When the bromoacetyl-thioester was used, inactivation was pH-dependent. The data are consistent with the competition of two processes, acylation, and alkylation. Direct (rather than secondary) alkylation of thiolase by the inactivator accounts for the significant 14C incorporation into thiolase with the thioester labeled with [14C] in the pantetheine pivalate moiety. It appears likely that the haloacetyl analogs described herein should be generally useful for affinity labeling other enzymes using acetyl-CoA as a substrate.

Acetyl Coenzyme A↗
PubMed1987

An unusual position of a Swan-Ganz catheter.

Placement of a Swan-Ganz catheter can cause many complications. This case report presents a new complication of Swan-Ganz catheter insertion--placement of the Swan-Ganz catheter tip in the coronary sinus.

Aged↗
PubMed1987

Echocardiographic estimate of left atrial pressure in children.

Echocardiographic estimates of left atrial pressure using the Q-MVC/AVC-E ratio were obtained from 21 patients in the early postoperative period and compared to simultaneously recorded mean left atrial pressure. A good correlation was obtained between mean left atrial pressure and the Q-MVC/AVC-E ratio (r = 0.81, p less than 0.001) with a regression equation of: left atrial pressure = 11.09 (Q-MVC/AVC-E) + 0.84. The present data compared to those of previous investigators reveal that, although there are quantitative differences between each of the studies, the correlation coefficient of each study is good. Echocardiography provides a useful noninvasive estimate the left atrial pressure; however, each laboratory must establish its own normals.

Blood Pressure↗
PubMed1987

Heyde's syndrome: failure of a mechanical prosthesis and the possibility of a coagulation defect.

Recent data indicate that the gastrointestinal bleeding due to angiodysplasia associated with aortic stenosis (Heyde's syndrome) can be alleviated by aortic valve replacement with a bioprosthesis. This report details a situation in which valve replacement with a mechanical prosthesis and the subsequent anticoagulation promoted gastrointestinal bleeding from angiodysplastic lesions. Only when the mechanical prosthesis was replaced with a porcine prosthesis and the anticoagulation discontinued did the gastrointestinal bleeding stop.

Anticoagulants↗
PubMed1986

Long-term follow-up of cardiac rhythm in repaired total anomalous pulmonary venous drainage.

Seven consecutive patients with total anomalous pulmonary venous drainage were operated at the Medical College of Ohio at Toledo and long-term follow-up is reported on their rhythm status. The patients were generally under 3 months of age at operation. All patients are alive at the present time. The median length of follow-up is 4 years. Five of the 7 patients demonstrated ectopic pacemaker activity and 2 exhibited episodes of nodal rhythm as well. In general, these were not apparent on standard screening electrocardiography. There was no correlation between the presence or absence of this arrhythmia and the type of repair. It is concluded that arrhythmias may be present in these patients, but that they are unrelated to the type of surgery performed. The ectopic atrial focus may be of no clinical significance but there is more cause for concern in those patients with nodal rhythm.

Arrhythmias, Cardiac↗