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Biomedical subjects

K W Lam

Publications and source records attributed to K W Lam.

At least 73 records · Page 4Linked to original sources
PubMed1986

Ocular hyperuricosis in the rabbit following hyperuricemia and topical epinephrine.

Sources for the high levels of uric acid reported in the aqueous humor from human glaucoma eyes were studied in the rabbit model. A hyperuricemia was produced by oxonic acid blockade of uricase prior to a systemic administration of uric acid. These animals showed no increase in aqueous humor uric acid. Topical medication of eyes with 1% epinephrine produced a statistically significant (P less than 0.001) rise in the level of uric acid in aqueous humor of treated eyes. Mean urate levels increased from 0.44 mg/dl to 0.82 mg/dl. Topical glaucoma medication appears to be the source of ocular hyperuricosis.

Administration, Topical↗
PubMed1986

Distribution of ascorbate in the retina, subretinal fluid and pigment epithelium.

The posterior segment of the eye was divided into four compartments: retinal cytosol (R), subretinal fluid on the retinal surface (S/R), retinal pigment epithelial (RPE) cytosol, and subretinal fluid on the RPE surface (S/RPE). The volume of each compartment was estimated from the dilution of creatinine (in the extraction buffer) by the endogenous tissue fluid. The ascorbate concentrations in R, S/R, S/RPE, and RPE were 20.6, 12.3, 3.7, and 5.8 mg/dl respectively. Dehydroascorbate was observed only in the RPE and S/RPE. The decreasing ascorbate concentration from the retina to RPE, and the distribution of dehydroascorbate suggest a movement of ascorbate from the vitreous cavity into the subretinal space. The permeability of retinal cell layers to ascorbate was confirmed by the high radioactivity observed in the subretinal space after an intravitreal injection of C14-ascorbate. The occurrence of dehydroascorbate in the RPE and the S/RPE indicates the presence of oxidative reaction of ascorbate in these compartments, where light induced free radicals are located.

Animals↗
PubMed1986

Acid phosphatase activity in mononuclear phagocytes and the U937 cell line: monocyte-derived macrophages express tartrate-resistant acid phosphatase.

Tartrate-resistant acid phosphatase (TRAcP) is used as a marker for osteoclasts, which are believed to be derived from phagocytic cells or phagocyte stem cell precursors. To further investigate the relationship between monocytic phagocytes and osteoclasts, acid phosphatase (AcP) activity was measured by three different techniques in human peripheral blood monocytes, monocyte-derived macrophages, and the U937 cell line. We found that cytochemistry and gel electrophoresis led to similar results, but that the colorimetric assay was inconsistent. Normal human peripheral monocytes expressed both tartrate-sensitive and -resistant AcP. In culture these cells formed polykaryons and expressed TRAcP activity that was further identified as an isoenzyme associated with bone tissue. In contrast, the U937 cells did not express TRAcP activity as measured by gel electrophoresis. Both U937 cells and monocytes possess material that interferes with interpretation of the colorimetric assay of AcP. The presence of TRAcP in monocyte-derived macrophages further supports the relationship between phagocytic cells and bone osteoclasts.

Acid Phosphatase↗
PubMed1986

Alteration of acid phosphatase isoenzyme in a human prostatic cancer cell line.

The acid phosphatase (AcP) isoenzyme in a human prostatic cancer cell line was compared to that of prostatic tissue extract by electrophoresis. The major isoenzyme by prostatic tissue extract is the AcP isoenzyme 2, while only AcP isoenzyme 4 (AcP-4) was observed in the human prostatic cancer cell line. A monoclonal antibody specific to AcP-4 was used to investigate the ultrastructural distribution of AcP-4 in a prostatic cancer cell line. The peroxidase staining pattern indicates that AcP-4 is synthesized on bound ribosomes, discharged into the cisternae of rough endoplasmic reticulum, transported to the cisternae of Golgi apparatus for concentration and packaging, and transferred to the secretory vesicles for exocytosis. It is well known that synthesis and secretion of AcP-2 are the major characteristics of the highly differentiated prostatic epithelial cells. The present data demonstrate the loss of this specific function in the prostatic cancer cell line. Instead of AcP-2, the dedifferentiated cancer cell line synthesizes and secretes AcP-4, which is a common AcP isoenzyme of many nonprostatic tissues.

Acid Phosphatase↗
PubMed1985

Immunoelectron microscopic demonstration of prostatic acid phosphatase in human hyperplastic prostate.

Immunoelectron microscopic studies were done on prostatic tissues obtained from patients with benign hyperplasia. Rabbit IgG-peroxidase conjugate against purified human prostatic acid phosphatase band 2 (HPAP-2) was used for studies. Under the light microscope, the columnar secretory epithelia of prostatic glands showed different intensity and distribution of immunostaining whereas the basal cells were unstained. Under the electron microscope, the secretory epithelial cells often showed electron-dense reaction product in the Golgi apparatus and secretory vesicles and vacuoles, and only sparingly in the cisternae of nuclear envelope and rough ER. Sometimes, fusion of secretory vacuolar membrane and plasma membrane and discharge of the vacuolar contents into the extracellular space were noted. The surfaces of microvilli at the apical portion of the columnar epithelia and the lumen of the glandular acini always showed reaction product. These findings suggest that HPAP-2 may be synthesized in the rough ER and transported to the Golgi apparatus where it is concentrated and transferred to the secretory vesicles and vacuoles. HPAP-2 is finally discharged into the extracellular spaces through exocytosis, a secretory mechanism similar to that of other secretory proteins.

Acid Phosphatase↗
PubMed1985

Distribution of retinoids in different compartments of the posterior segment of the rabbit eye.

Using high-performance liquid chromatography, the amounts of all-trans retinol, retinal and retinyl palmitate were measured in the following ocular tissues and fluid of the light (LA) and dark adapted (DA) rabbit: cytosol and membrane fractions of the retina (R/C and R/M), cytosol and membrane fractions of the retinal pigment epithelium (RPE/C and RPE/M), subretinal fluid collected from the inter-photoreceptor matrix (S/R) and the matrix between apical microvilli of the RPE (S/RPE). The total amount of all-trans retinol extracted from LA eyes, 2.74 nmol per eye, was ten times greater than the amount extracted from DA eyes. In the LA eye, most of the all-trans retinol was extracted from the membrane fraction of the retina (67%); in the DA eye, most of the retinol was extracted from the cytosol fraction of the retina (58%). In contrast, the DA eye yielded more all-trans retinal (9.84 nmol) than the LA eye (5.80 nmol) and most of this retinoid was recovered from the cytosol and membrane fractions of the retina. A higher amount of all-trans retinyl palmitate was recovered from the LA eye (5.88 nmol) than the DA eye (2.02 nmol). Although most of this retinyl palmitate was extracted from the cytosol fraction of the RPE (45%, LA eye), appreciable amounts were found in all other ocular compartments. The amount of retinyl palmitate in the LA eye exceeded that of the DA eye in every compartment examined in the present study, suggesting a possible important role of retinyl esters in the visual cycle.

Animals↗
PubMed1985

Immunohistochemical detection of monocytes by the antiserum specific to monocytic esterase.

An antiserum specific to esterase Ib was produced in a rabbit. The antigen-antibody reaction was visualized by the strong esterase activity in the precipitin band in Ouchterlony double diffusion and immunoelectrophoresis. Immunohistochemical procedure demonstrated strong staining in the monocyte-infiltrated splenic sections and tissue sections of true histiocytic lymphoma. Negative results were observed in T- and B-cell lymphomas, granulocytic sarcoma, and chronic granulocytic leukemia. This antibody may be useful for the identification of monocytes and histocytes in paraffin-embedded tissue sections.

Animals↗
PubMed1985

Simultaneous demonstration of nonspecific esterase and chloroacetate esterase in human blood cells.

A new cytochemical method is described for the simultaneous demonstration of nonspecific esterase in monocytes and chloracetate esterase in granulocytes. The procedure uses both alpha-naphthyl butyrate and naphthol AS-D chloroacetate as substrates and hexazotized pararosaniline as the coupler. The enzyme reaction products are highly chromogenic and their localization is precise. This method is potentially useful for the accurate diagnosis of the acute monocytic leukemias. Its advantages and limitations are also discussed.

Acute Disease↗
PubMed1984

Distribution of ascorbate in normal primate retina and after photic injury: a biochemical, morphological correlated study.

The levels of reduced and oxidized ascorbates were determined in the normal baboon neural retina and pigment epithelium-choroid. The ascorbate in the neural retina was mainly in the reduced form, while in the pigment epithelium, it existed primarily in the oxidized form. One eye of each of six baboons was exposed to indirect ophthalmoscope light for 30 minutes. Morphologic study showed necrotic photoreceptors, outer segment disorganization, and abnormal pigment epithelial basal infoldings and swollen microvilli. After the light exposure, the values of the reduced ascorbate decreased in both the neural retina and pigment epithelium-choroid of the posterior pole. The possible role of ascorbate as an antioxidant and ascorbate transport into the retina are discussed.

Animals↗
PubMed1984

Inhibition of oxidative degradation of hyaluronic acid by uric acid.

It has been postulated that glycosaminoglycans in the trabeculum have an influence on aqueous humor drainage. Ascorbate reduces the viscosity of hyaluronic acid, and also increases outflow facility. Our recent observation of high urate concentrations in some glaucomatous eyes led us to study the influence of urate on oxidative degradation of hyaluronic acid by ascorbate. The viscosity of rooster comb hyaluronic acid was reduced slowly by ascorbate. Cupric sulfate accelerated ascorbate oxidation and also enhanced hyaluronic acid degradation. Urate inhibited ascorbate oxidation and prevented the copper catalyzed oxidative degradation of rooster comb hyaluronic acid. The range of urate concentrations used in this study was within the range of urate concentrations observed in glaucomatous eyes. The partially purified umbilical cord hyaluronic acid had lower viscosity than rooster comb hyaluronic acid, and rapidly degraded in the presence of ascorbate. The ascorbate effect on umbilical cord hyaluronic acid was partially prevented by urate.

Animals↗
PubMed1984

Tartrate-resistant acid phosphatase in serum of cancer patients.

Tartrate-resistant acid phosphatase activity determined by enzyme immunoassay was higher in the serum of cancer patients than that in normal blood donors. The highest activity was found among patients having malignancy metastatic to bone. The classic colorimetric method showed a broad range of values among normal blood donors, and the contrast between normal and cancer patients was less obvious. Most of the cancer patients had normal to low alkaline phosphatase activities.

Acid Phosphatase↗
PubMed1983

Prostatic cancer presenting as metastatic adenocarcinoma of undetermined origin. Immunodiagnosis by prostatic acid phosphatase.

Adenocarcinoma of the prostate may occasionally present as distant metastatic disease. This tumor, if accurately identified, is amendable to effective treatment with hormonal manipulations. We have seen nine patients with prostatic cancer presenting as metastatic adenocarcinoma of undetermined origin: two presented with involvement in the lung and the mediastinum, five with left supraclavicular lymphadenopathy and two with known prostatic cancer with stable disease presented with supraclavicular lymphadenopathy. By employing an immunoperoxidase technique using prostatic acid phosphatase as the marker for the prostatic cells, we demonstrated the presence of the prostatic enzyme antigen in the paraffin embedded tissues from the metastatic tumor. This finding directed further investigation of the prostate gland leading to the discovery of the primary tumor in all nine patients. It may be beneficial to use this technique in all male patients with adenocarcinoma of undetermined primary site.

Acid Phosphatase↗
PubMed1983

Reduced and oxidized ascorbates in guinea pig retina under normal and light-exposed conditions.

Both reduced and oxidized ascorbates were measured in aqueous, neural retina, and pigment epithelium-choroid complex (PE-C) of pigmented guinea pigs. Normal values for total ascorbate of 16 mg/dl in aqueous, 22 mg/dl in neural retina, and 7 mg/dl in PE-C were found. After mild photic damage caused by varying lengths of exposure of 10,000 to 20,000 lux of fluorescent lighting, reduced ascorbate concentrations generally decreased in the neural retina, while oxidized ascorbate generally increased in PE-C. In both normal and light-exposed retinas, reduced ascorbate was predominant in the neural retina, and oxidized ascorbate was predominant in the PE-C. Histochemical localization of reduced ascorbate occurred in the Müller cell fibers and at the apices of the retinal pigment epithelium.

Animals↗
PubMed1982

Source of subretinal fluid on the basis of ascorbate analyses.

Biochemical analyses of subretinal fluid revealed a consistently high ascorbate level in the subretinal fluid of patients with rhegmatogenous retinal detachment. The average values and SDs of ascorbate in anterior chamber aqueous humor, subretinal fluid, and blood were 14.7 +/- 1.8, 27.4 +/- 2.1, and 1.8 +/- 0.2 mg/dL, respectively. The ascorbate concentration in subretinal fluid was always higher than that in aqueous humor. The high ascorbate level in subretinal fluid led to the hypothesis that aqueous humor contributes to the formation of subretinal fluid. Presumably and constant absorption of subretinal fluid by the choroid directs a portion of the aqueous humor from the posterior chamber into the subretinal space. The posterior movement of aqueous humor causes reduced ascorbate concentration in the anterior chamber and relative hypotony of eyes with rhegmatogenous retinal detachment. Closing the retinal break results in an interruption of the posterior movement of aqueous humor and rapid absorption of the remaining subretinal fluid by the choroid.

Aqueous Humor↗
PubMed1982

Comparison of prostatic and nonprostatic acid phosphatase.

Electrophoresis and ion-exchange column chromatography were used to separate the wide varieties of acid phosphatases with different biological and clinical significance. Band 0 was very strong in ascitic cells with many autophagic vacuoles, indicating a role in autophagic function. Band 1 was a membrane-bound acid phosphatase, seen mainly in the microsomal fraction. Band 3 was the major lysosomal acid phosphatase of all nonprostatic tissues. Bands 2 and 4 were antigenically identical to each other, and were observed in unusually high amounts in the prostate. The different electrophoretic mobility between bands 2 and 4 was due to their carbohydrate content. Band 5 was a characteristic enzyme of the osteoclast. The tartrate-sensitive enzymes included bands 0 through 4. Only band 5 was tartrate resistant. The tartrate-resistant acid phosphatase of erythrocytes was not detected by the electrophoresis method. Clinical applications were seen for both bands 2 and 5. Band 2 was a secretory enzyme, normally secreted into the seminal plasma. Band 2 was absorbed into the blood circulation in some prostatic cancer patients. A small amount of bands 2 and 4 was observed in nonprostatic tissues. The diagnostic value of band 2 resulted from its extremely high concentration in the prostate. Band 5 was not observed in the normal prostate. A high concentration of band 5 was observed in hairy cells, Gaucher cells, and osteoclasts. The serum level of band 5b was an indicator of osteoclastic activity in the bone. Elevation of band 5b in serum was observed in normal children during physiological bone growth, in Gaucher's disease, and in malignancies metastasized to bone.

Acid Phosphatase↗