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Biomedical subjects

M Lin

Publications and source records attributed to M Lin.

At least 343 records · Page 19Linked to original sources
PubMed1990

Primary adenocarcinoma of the female urethra with three histologic patterns and partial AFP positivity.

A rare case of adenocarcinoma of the female urethra with alpha-fetoprotein (AFP) positivity in a 52-year-old woman is reported. The tumor was papillary polypoid, localized in the posterior wall of the mid-urethra and microscopically showed three histologic components. Upon immunostaining and histochemical staining, the tumor was characterized by intestinal-type cells positive for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), EMA-negative and AFP-positive columnar vacuolated cells and mainly EMA-positive clear cells. On the basis of these features together with the known embryogenesis of the urethra, an endodermal origin of the tumor is suggested, possibly arising from the reserve or stem cells in the urethral mucosa. This case and its immunohistochemical features are quite unique and the histologic combination is meaningful when considering the oncogenesis and histogenesis of urethral tumors.

Adenocarcinoma↗
PubMed1990

Stimulation of protein secretion in the initial segment of the rat epididymis by fluid from the ram rete testis.

Zone 1A of the ductus epididymidis was perfused with ovine rete testis fluid (nRTF) and modifications of it, and a synthetic medium (sRTF) based on the inorganic composition of nRTF. There was little fluid transport by the duct mucosa and nRTF stimulated protein secretion. The secretagogue activity was not extracted by charcoal, was sensitive to protease digestion and was present in a portion of nRTF with a molecular weight of greater than 10,000. The addition of bovine serum albumin to the sRTF stimulated protein secretion, but not to the same extent as equal amounts of protein in nRTF. Polyacrylamide gel electrophoresis of the perfusates showed that proteins with molecular weights of 19,000 (all rats studied), and 22,000, 30,000 and 60,000 (at least half the rats studied) were secreted into the perfusion fluids as well as some blood proteins, but the pattern of secretion was not affected by the composition of the perfusion fluid.

Animals↗
PubMed1990

The cycle of the seminiferous epithelium in the Japanese quail (Coturnix coturnix japonica) and estimation of its duration.

A regular, well defined spermatogenic cycle was found in the Japanese quail by examining thin sections of isolated lengths of seminiferous tubules embedded in epoxy resin to resolve the structure of developing spermatids. The stages of the cycle initially were identified in studies using a preparatory method for fixation which separated adjacent cellular associations. The cycle was divided into 10 stages with relative frequencies (%) of Stages I to X respectively of: 11.9, 14.8, 24.1, 10.3, 8.2, 6.4, 9.4, 5.5, 3.8 and 5.4. The duration of one cycle was 2.69 +/- 0.08 days (mean +/- s.e.m.) as determined by intraventricular injection of [3H]thymidine and autoradiographic examination of the testes 1-4 days later. It was estimated that lifespans were 2.01 days for type B spermatogonia, 3.86 days for primary spermatocytes, 0.15 days for secondary spermatocytes, and 4.54 days for spermatids. The results suggest that the kinetics of spermatogenesis in the quail are fundamentally similar to the pattern in mammals.

Animals↗
PubMed1990

Spatial arrangement of the stages of the cycle of the seminiferous epithelium in the Japanese quail, Coturnix coturnix japonica.

The spatial arrangement of the stages of the cycle of the seminiferous epithelium of the Japanese quail was investigated by preparing three-dimensional reconstructions of a seminiferous tubule from each of 3 quails. It was found that the stages were not distributed at random, but were arranged in a wave which spiralled helically along a seminiferous tubule. Adjacent stages in space were always adjacent numbers in the cycle of the seminiferous epithelium. Complete spermatogenetic waves were found in which all 10 stages of the cycle were in sequential order. However, in most waves the sequential order of stages was disturbed by the occurrence of modulations. The area of a cellular association varied from 4600 to 41,600 microns 2 with a mean +/- s.e.m. (3 animals) of 17,902 +/- 2614 microns 2. The number of Sertoli cells involved in an association ranged from 4 to 35, with a mean +/- s.e.m. (3 animals) of 13.5 +/- 2.8. The findings support our earlier suggestion that the kinetics of spermatogenesis in the quail are fundamentally similar to the pattern which has been described for mammals.

Animals↗
PubMed1989

Pyruvate kinase isozymes from the green alga, Selenastrum minutum. I. Purification and physical and immunological characterization.

Pyruvate kinase from the green alga Selenastrum minutum consists of two isoforms (PK1 and PK2) separable by Q-Sepharose chromatography. The two isoforms have been highly purified to respective final specific activities of 42 and 23 (mumol pyruvate produced/min)/mg protein. Purification steps included salt fractionation, anion-exchange, hydrophobic interaction, and gel filtration chromatography. The final enzyme preparations differ significantly in physical and immunological properties. PK1 is heat labile and is completely inactivated following reaction with N-ethylmaleimide. In contrast, PK2 is heat-stable and is only partially inactivated following N-ethylmaleimide treatment. PK1 appears to be homotetrameric with a native molecular mass of about 240 kDa, whereas PK2 appears to be homodecameric with a native molecular mass of approximately 590 kDa. The antigenic reaction of both final PK preparations to rabbit antiserum prepared against homogeneous germinating castor bean endosperm cytosolic pyruvate kinase was tested by immunoprecipitation and Western blotting. The two algal pyruvate kinases are immunologically unrelated as only PK2 cross-reacts with the cytosolic pyruvate kinase antibodies. These data indicate that the S. minutum pyruvate kinase isoforms, PK1 and PK2, are not interconvertible forms of the same protein, but probably represent chloroplastic and cytosolic isozymes, respectively.

Ammonium Sulfate↗
PubMed1989

Pyruvate kinase isozymes from the green alga, Selenastrum minutum. II. Kinetic and regulatory properties.

The kinetic and regulatory properties of two pyruvate kinase isozymes, PKp and PKc (apparent chloroplastic and cytosolic isozymes, respectively) from the green alga Selenastrum minutum were studied. The two isozymes differed greatly in several kinetic properties. Although both isozymes showed hyperbolic substrate saturation kinetics, the apparent Michaelis constants for PEP and ADP were about twofold and fourfold lower, respectively, for PKc as compared with PKp. ADP was the preferred nucleotide substrate for both isozymes. However, PKc utilized alternate nucleotides far more effectively than did PKp. PKc and PKp also differed strongly in the effect of activators and inhibitors on the enzymes. Although both isozymes were activated by dihydroxyacetone phosphate (DHAP) with a similar activation constant of about 30 microM, this activator (0.5 mM) caused an approximate 30% increase in the Vmax of PKc, but had no effect on the Vmax of PKp. PKp, but not PKc, was inhibited by ribose 5-phosphate, ribulose 1,5-bisphosphate, 2-phosphoglycerate, phosphoglycolate, and malate. Both isozymes were inhibited by MgATP, Mg2citrate, Mg2oxalate, and Pi. PKc was far more sensitive to inhibition by Pi, as compared with PKp. Pi was a competitive inhibitor of PKc with respect to phosphoenolpyruvate (PEP) (Ki = 1.3 mM). Glutamate was a potent inhibitor of PKc, but had no effect on PKp. In contrast with Pi, glutamate was a mixed-type inhibitor of PKc with respect to PEP (Ki = 0.7 mM). DHAP facilitated the binding of PEP by both isozymes and reversed or relieved the inhibition of PKc by Pi and/or glutamate. The regulatory properties of PKp indicate that it is likely less active in the light and more active in the dark. The in vivo activity of PKc is probably regulated by the relative cytosolic levels of DHAP, Pi, and glutamate; this provides a rationale for the activation of algal cytosolic pyruvate kinase which occurs during periods of enhanced ammonia assimilation.

Adenosine Diphosphate↗
PubMed1989

MR imaging of neurocysticercosis.

Twenty-six patients with neurocysticercosis were studied with MR imaging to correlate their clinical presentation with the location and appearance of their neurocysticercosis lesions. Intraventricular cysts were present in 14 patients (54%), parenchymal cysts were present in 18 (69%), and intraventricular together with parenchymal cysts were present in six (23%). Intraventricular cysts were detected by mass effect, ventricular obstruction, detection of a cyst rim, and/or CSF flow void adjacent to the cyst. The intensity of most intraventricular and parenchymal cysts presumed to be viable was similar to that of CSF on both T1- and T2-weighted sequences. Cysts presumed to be degenerated had increased signal intensity on T1-weighted images, probably resulting from increased protein content. Pericystic high signal intensity surrounding lesions of various ages was seen on both proton-density- and T2-weighted images and represents gliosis, edema, and inflammation. Patients with parenchymal cysts had symptoms of seizures, while those with intraventricular cysts generally had symptoms related to obstructive hydrocephalus. Aqueductal stenosis, seen in 10 patients (38%), was possibly due to ependymal inflammation or adhesions caused by prior ventricular infection by neurocysticercosis. One patient with the racemose form of neurocysticercosis demonstrated abundant cyst wall proliferation resulting in obstructive hydrocephalus. In six patients scanned 1-6 months after oral praziquantel therapy, there was no change in the MR appearance of intraventricular cysts, while some parenchymal cysts showed evidence of degeneration. We found MR to be useful in detecting the cysts of neurocysticercosis and the accompanying signs of cyst degeneration and pericystic inflammation. MR was inferior to CT in the detection of parenchymal calcifications.

Adolescent↗
PubMed1989

[Application of the finite element method to craniofacial growth analysis. 4. Three-dimensional application of tensor analysis].

The purpose of this study is the 3-dimensional application of finite element method to analyze the craniofacial growth. In our previous studies, 2-dimensional finite element method was applied to analyze and to predict the craniofacial growth. In case of 2-dimensional application, the normal and shear strains were given by the displacements u, v that were linear functions of coordinates x, y. In the 3-dimensional case, six strain components are required to obtain the extension ratio and the directions of three-principal axes. In this study, for the 3-dimensional application, four-noded, pyramidal elements were used and twelve 3-dimensional elements were constructed. Materials were longitudinal frontal and lateral cephalometric X-rays of 4 males and 4 females from 7 to 10 years with normal occlusions. 3-dimensional coordinates of each nodal points were calculated by transforming 2-dimensional coordinates on the frontal and lateral cephalometric X-ray films. Coordinates of the nodal points at 7 years were standards against that results of the finite element method from 8 to 10 years were obtained. They were subjects of the analysis that elements equivalent to the cranial base, the maxillary portion, the maxillary alveolar portion and the posterior pharyngeal portion. Summarized results were as follows. 1. It was observed that the similar figured extension of the anterior cranial base element. 2. The posterior cranial base element extended to right, anterior and upwards direction. 3. On the maxillaly elements, especially, lateral extensions appeared. 4. The element of the posterior pharyngeal portion extended to left and downwards direction. 5. The elements of the maxillary alveolar portion extended to downwards directions. From the above, the directions of transformation of the elements that are selected with voluntary nodal points can be observed. Therefore, 3-dimensional tensor analysis is a method of great significance for obtaining new findings of the craniofacial growth.

Cephalometry↗
PubMed1987

cDNA probes of individual genes of human rotavirus distinguish viral subgroups and serotypes.

The use of cDNA probes for detection of rotaviruses has been investigated using plasmids containing inserts specific for each of the eleven genes of human rotavirus strain Wa. In a dot-blot detection system in which radioactive DNA probes were hybridized to viral RNA extracted from cultivatable rotavirus strains, cDNAs of genes 7, 8, 10 and 11, were found to be the most reliable probes for detecting a range of rotavirus strains. Unexpectedly, rotaviruses could be distinguished with respect to subgroup and subtype specificities when cDNAs of genes 6 and 9, which encode the immunologically relevant proteins VP6 (group-specific antigen) and VP7 (type-specific antigen), were used as probe, even though the nucleic acid sequences of these genes are known to have a high degree of sequence homology.

Child, Preschool↗