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Biomedical subjects

G H Yu

Publications and source records attributed to G H Yu.

52 records · Page 3Linked to original sources
PubMed1989

[Influence of total parenteral nutrition on amikacin pharmacokinetics].

Six patients under total parenteral nutrition (TPN) and eight control patients received 200 mg of amikacin by iv infusion in 0.5 h. Amikacin concentrations of serum and urine were determined by fluorescence polarization immunoassay. At 6 h after the beginning of administration, the amikacin level in serum of TPN group (2.3 +/- 0.8 micrograms/ml) was significantly higher than control (1.3 +/- 0.8 microgram/ml). There was no significant difference between the 24-h urine output of 2 groups. Pharmacokinetic calculations were based on a two-compartment open-system model. The T1/2 beta and apparent volumes of distribution (Vc, Vdss, V2) of TPN group were significantly greater than those of control group. The body clearance of amikacin in TPN group was slower than control. It is suggested that serum amikacin concentrations should be monitored in clinical TPN patients to prevent toxic reactions.

Adult↗
PubMed1988

Biochemical characterization of membrane cofactor protein of the complement system.

Membrane cofactor protein (MCP; formerly termed glycoprotein 45-70 to indicate its Mr) of complement is a widely distributed iC3/C3b binding protein with co-factor activity. On human mononuclear cells and cell lines and platelets, MCP is a doublet. The two forms differ in Mr by approximately 5 k and the upper species is predominant in most individuals. To further characterize these two forms, limited proteolytic digestions were performed. Of the four peptides produced, three have identical Mr indicating that the molecules are similar proteins. Both forms also have acidic isoelectric points and shift to a less acidic isoelectric point after treatment with neuraminidase. Glycosidase digestions indicate that both species contain N- and O-linked oligosaccharides but that the quantity of sialic acid is greater on the larger one. Pulse-chase experiments demonstrate approximately equal quantities of two precursor forms with Mr of 41 and 43 k. These two precursors possess N-linked high-mannose type of oligosaccharides and chase into the mature molecules which have complex sugars. The smaller precursor chases at a slower rate, possibly accounting for the reduced quantity of the smaller form of the mature form of MCP. These experiments indicate that the two forms of MCP are structurally similar and are derived from two distinct precursors. They also suggest that variations in the rate of processing of two intracellular precursors may account for the different quantities of the mature forms of this membrane protein.

Antigens, CD↗
PubMed1986

Identification of a third component of complement-binding glycoprotein of human platelets.

Utilizing affinity chromatography, a C3-specific binding protein was isolated from 125I surface-labeled human platelets. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated two bands with mean Mr of 64,000 and 53,000, characteristic variability in the relative density of the two bands in a given individual, and the presence of N-linked complex oligosaccharides as well as sialic acid residues not associated with N-linked sugars. These characteristics are similar to those of a human leukocyte iC3- and C3b-binding glycoprotein, termed gp45-70. Further analysis showed that leukocyte gp45-70 and the platelet C3-binding glycoprotein have identical Mr and other similar structural features. Functional characterization of solubilized platelet preparations indicated that gp45-70 has cofactor activity. This membrane glycoprotein is structurally and antigenically distinct from decay accelerating factor (DAF), a complement regulatory protein previously identified on human platelet membranes. DAF and gp45-70 have complementary activity profiles inasmuch as DAF can prevent assembly of and dissociate the C3 convertases but has no cofactor activity, whereas gp45-70 has cofactor activity but no decay accelerating activity. We suggest that these two proteins function conjointly to prevent autologous complement activation.

Blood Platelets↗
PubMedDate not supplied

Structural requirements for binding of adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) to human neutrophils.

Human polymorphonuclear leukocytes (PMN) respond via pertussis toxin-sensitive pathways to extracellular nucleotides with an elevation in intracellular calcium ([Ca2+]i) and enhancement of the O2- generation induced by the chemotactic peptide N'-formyl-Met-Leu-Phe (fMLP). Binding studies with adenosine 5'-O-(3-thio[35S]triphosphate) ([35S]ATP gamma S) have recently identified at least two classes of receptors on intact human neutrophils. In this study, we further characterize nucleotide binding to this receptor with respect to its specific structural requirements. Utilizing [35S]ATP gamma S as the primary ligand and various nucleotides and ATP analogues, competitive binding studies demonstrate that: (1) the triphosphate tail is essential for maximal receptor binding; (2) chemical modifications of the phosphate tail have profound effects on binding efficacy; (3) the base ring is recognized by the receptor, with purines being preferentially recognized; and (4) except for a spacing function, the ribose ring of nucleotides does not appear to be important for nucleotide binding. In addition, we demonstrate that the presence of divalent cations inhibits [35S]ATP gamma S binding, suggesting that the tetraanionic form of ATP (ATP4-) is the nucleotide species reactive with the receptor.

Adenine Nucleotides↗
PubMedDate not supplied

The immediate postconization endocervical smear: evaluation of its utility in the detection of residual dysplasia.

OBJECTIVE: To determine the diagnostic value of obtaining an endocervical smear for cytologic examination immediately following cervical conization (by either the loop electrosurgical excision procedure or large loop excision of the transformation zone) in the detection of residual squamous dysplasia. STUDY DESIGN: Thirty-eight cases were identified in which cervical conization was immediately followed by endocervical sampling (most commonly using a brush) and smear. RESULTS: Twenty-one of the 38 postconization endocervical smears (55%) were either unsatisfactory or sub-optimal for evaluation due to cellular distortion (i.e., cautery artifact), degeneration or obscuring blood. Histologic in evaluation showed negative endocervical margins in 32 cases (84%) and positive endocervical margins in 6 cases (16%), including both low and high grade squamous intraepithelial lesions. The endocervical smears in the 32 cases with a negative surgical margin did not demonstrate evidence of dysplasia. However, in the six cases with histologically positive margins, postconization endocervical smears also failed to identify any evidence of dysplasia. CONCLUSION: Immediate postconization endocervical smears do not appear to be useful for the detection of residual disease in patients undergoing conization for squamous dysplasia of the cervix.

Adolescent↗
PubMedDate not supplied

Cytologic grading of fine needle aspirates of breast carcinoma by private practice pathologists.

OBJECTIVE: To determine the reproducibility of two clinically proven grading systems for breast carcinoma assessed by private practice pathologists. STUDY DESIGN: Twenty fine needle aspiration (FNA) slides of histologically proven breast carcinoma were submitted to 15 private practice pathologists practicing in 11 separate groups who interpret cytology as part of their daily practice. The pathologists received the same set of slides. They graded the FNAs using the modified Black (MB) (grades 1-3) and simplified Black (SB) (low grade, high grade) grading systems. Specified criteria and guidelines as well as case samples were provided. RESULTS: There was complete agreement among the 15 pathologists on only one case using the MB grading system as compared to five using the SB grading system. In MB, > or = 10 pathologists were in agreement on 14 cases as compared to 19 cases using SB. There were three cases in MB where the grades ranged from 1 to 3. Also noted in MB was the high number of cases graded 2 (intermediate grade). The predominant comment made by the pathologists was the easier, more objective and practical application of the SB. CONCLUSION: High reproducibility in the cytologic grading of FNA of breast carcinoma can be more readily attained among private practice pathologists using the two-tier SB grading system.

Biopsy, Needle↗
PubMedDate not supplied

Role of cytology in the intraoperative diagnosis of HIV-positive patients undergoing stereotactic brain biopsy.

OBJECTIVE: To determine the accuracy of cytology in the intraoperative diagnosis of central nervous system (CNS) lesions in human immunodeficiency (HIV)-positive patients. STUDY DESIGN: We prospectively studied 75 cases of computed tomography- or magnetic resonance imaging-guided brain biopsies performed with stereotactic instrumentation and a Nashold biopsy cannula over the course of five years. Biopsy samples were sent for both frozen section and immediate cytologic evaluation. Crush preparations (Papanicolaou and Diff-Quik stained) were used for cytologic assessment. There were 23 cases of progressive multifocal leukoencephalopathy (PML), 8 of toxoplasmosis (toxo), 3 of herpes simplex virus, 26 of lymphoma, 3 of HIV encephalitis, 1 of melanoma, 1 of hamartoma and 10 of nonspecific changes (paraffin section). RESULTS: Using permanent hematoxylin and eosin-stained histologic sections as the "gold standard," frozen section had a sensitivity of 78% and a specificity of 90%, while cytology had a sensitivity of 88% and specificity of 90%. Most of the false negative cases in cytology and frozen section were due to the predominance of necrosis and/or gliosis, present in six cases of toxo. Two of the false positive cases in frozen section (diagnosed as lymphoma) showed toxo, while two false positive cases in cytology (diagnosed as PML) showed only gliosis with negative immunoperoxidase staining for PML in the permanent sections. CONCLUSION: First, cytology had higher sensitivity that frozen section. Second, cytology provided faster results in most instances, primarily due to the nature of specimen preparation. Third, most misdiagnoses occurred in infectious diseases, especially toxo; this should therefore be kept in mind when nonspecific changes with an atypical lymphocytic infiltrate are seen. Fourth, cytology can be an alternative to frozen section for the intraoperative diagnosis of CNS lesions in HIV-positive patients. Another advantage of cytology is elimination of the need for cutting potentially infectious fresh tissue.

Biopsy↗
PubMedDate not supplied

Benign pairs. A useful discriminating feature in fine needle aspirates of the breast.

OBJECTIVE: To determine the diagnostic utility of the finding of naked, bipolar nuclei in fine needle aspirates of breast lesions. STUDY DESIGN: Aspirate smears from 150 cases of histologically proven benign (77) and malignant (73) breast lesions were evaluated for the presence of stripped, bipolar nuclei in the smear background as singlets as well as closely associated pairs. RESULTS: The presence of such pairs was a more specific indicator of benign entities (present in 70% of benign lesions vs. 1% of carcinomas) when compared to single, bare nuclei alone (present in 94% of benign lesions vs. 45% of carcinomas). Large numbers of such "benign pairs" also strongly favored the diagnosis of fibroadenoma within the benign subgroup. CONCLUSION: The presence of bipolar nuclear pairs is a valuable addition to the finding of singlets in the diagnosis of benign breast lesions and their subclassification.

Adenocarcinoma↗
PubMedDate not supplied

Fine needle aspiration biopsy of the salivary glands. A five-year experience with emphasis on diagnostic pitfalls.

OBJECTIVE: To review the fine needle aspiration (FNA) findings in 151 patients who presented with salivary gland (both major and minor) enlargement from January 1991 to December 1995 in order to determine its sensitivity and specificity and to study the various pitfalls. STUDY DESIGN: The study group consisted of 77 males and 74 females, 16-98 years old (average 55). One hundred twenty-five aspirates (83%) were from the parotid gland, 23 (15%) from the submandibular gland and 3 (2%) from the soft palate. One hundred thirty-seven cases (91%) were adequate for diagnosis. There were 89 (59%) aspirations done by cytopathologists, 100% of which were diagnostic, and 62 (41%) done by clinicians, 48 (77%) of which were diagnostic. Sixty-eight (45%) cases had histologic confirmation. There were 104 (75.9%) benign, 20 (14.6%) malignant and 13 (9.5%) atypical cytologic diagnoses. RESULTS: Using histology as the "gold standard," the sensitivity of FNA cytology was 91%, with a specificity of 96%. A number of problems were encountered in interpreting some cases, not only in differentiating benign from malignant ones but also in the specific classification of these neoplasms. Problems encountered involved differentiating hematopoietic from non-hematopoietic lesions and interpretation of spindle cell neoplasms, acinic cell carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma, lymphoproliferative disorders, postirradiation changes, sialadenitis and atypia in pleomorphic adenoma. CONCLUSION: FNA biopsy of the salivary gland is a sensitive and specific diagnostic tool at our institution. Particular attention to subtle morphologic changes may aid in avoiding pitfalls and arriving at the right diagnosis.

Adenoma, Pleomorphic↗