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Biomedical subjects

K J Fan

Publications and source records attributed to K J Fan.

17 recordsLinked to original sources
PubMed2000

Polyomavirus JC genotypes in an urban United States population reflect the history of African origin and genetic admixture in modern African Americans.

The human polyomavirus JC (JC virus), a small, circular, double-stranded DNA virus, has a worldwide distribution and is excreted harmlessly in urine by 20% to 70% of adults. DNA sequence analysis has identified seven distinct genotypes that likely coevolved with modern humans, although the mode of virus transmission is unknown. Type 1 is European in its distribution. Types 2 and 7 are Asian, while Types 3 and 6 are African. Type 4, closely related to Type 1, is of uncertain origin, having been found in population groups in parts of Europe and in the United States, but not in Africa. Here we have studied the JCV partial genomic DNA sequences amplified by polymerase chain reaction techniques from urines of an urban, mainly African American population cohort from Washington, D.C. The predominant genotype identified was Type 4 (32/78 JCV strains, 41%). Type 1 strain was found in 32% of African Americans, while JCV Type 3 strain was found in 18% of African Americans. These African strains have persisted in modern African Americans after 200 to 400 years of minority existence and genetic admixture in the New World. An ancient West African genotype, Type 6, was absent in this African American cohort. However, one Type 6 strain was found in a patient from Sierra Leone (West Africa), domiciled in the United States for 20 years. Type 2A, the most common subtype in Native Americans, was seen in only two African-Americans (3%). A Type 7 strain, previously reported only in Taiwan and South China, was identified in a Vietnamese immigrant. These data support the history of African origin, migration, and genetic admixture of modern African Americans. Analysis of JCV strains in the present American populations provides a novel tool for reconstructing human migrations and genetic admixture in the New World.

Adolescent↗
PubMed1992

Ethnic distribution of primary central nervous system tumors in Washington, DC, 1971 to 1985.

An ethnic analysis was made of 8947 cases of primary central nervous system (CNS) tumors seen at the Armed Forces Institute of Pathology (AFIP), Washington, DC, from 1971 to 1985. Results showed a slightly higher frequency of primary CNS tumors in whites than in blacks with a white:black case ratio of 9:1 against the white:black population ratio in the United States of 7.4:1. Gliomas appeared to be twofold more frequent in whites than in blacks with a white:black case ratio of 12.1:1. However, meningiomas and pituitary adenomas were more common in blacks with a white:black case ratio of 6.7:1 and 4.2:1, respectively. When these results were compared with the results of a previous identical study using similar materials collected at AFIP from 1958 to 1970, the relative paucity of gliomas and higher frequency of meningiomas and pituitary adenomas in American blacks is again confirmed, thus re-emphasizing the importance of genetic factors in the genesis of primary CNS tumors. The remarkable decreasing white:black case ratio of primary CNS tumors as a whole (9:1 compared with 13.7:1) since 1970 probably reflects the socioeconomic improvement of American blacks during the same period.

Adult↗
PubMed1991

The nucleus basalis of Meynert, senile plaques, and intellectual impairment in schizophrenia.

The large, hyperchromic, cholinergic neurons of the nucleus basalis of Meynert (nbM) and the presence of senile plaques were quantified in postmortem brain tissue from 10 intellectually impaired schizophrenic patients, seven intellectually intact schizophrenic patients, seven control subjects, and three patients with Alzheimer's disease. The two groups of schizophrenic patients did not show any significant differences when compared with the control group in nbM cell density or in plaque frequency. The Alzheimer's disease patients showed the expected decrease in nbM neuronal density and increase in plaques compared with the controls. The data suggest that compromised cognitive function in schizophrenia is not associated with diffuse neuropathology of the basal forebrain cholinergic system.

Acetylcholine↗
PubMed1990

Estimation of microscopic redox potentials of a tetraheme protein, cytochrome c3 of Desulfovibrio vulgaris, Miyazaki F, and partial assignments of heme groups.

The microscopic formal redox potentials of a tetraheme protein, cytochrome c3 from Desulfovibrio vulgaris, Miyazaki F, were estimated from the chemical shifts of the heme methyl signals in its 1H NMR spectrum. All chemical shifts in the five macroscopic oxidation states were determined for eight of the heme methyl protons by the saturation-transfer method. The electron-distribution probability at each heme in each oxidation state was estimated directly from the chemical shifts. To minimize errors due to interheme pseudocontact contributions, the average electron-distribution probability was used for calculation of the microscopic formal redox potentials. By introducing interacting potentials, 32 parameters were reduced to 10. The 10 parameters were determined analytically from the 9 independent electron-distribution probabilities and 2 macroscopic formal redox potentials. The results showed the presence of a strong positive interaction between a pair of particular hemes. The microscopic formal redox potential changes dramatically with the extent of reduction because of the intramolecular interheme interactions. NMR signals of two hemes were assigned to particular hemes in the crystal structures by nuclear Overhauser effect experiments. The results showed that the hemes with the highest and lowest redox potentials in the one-electron reduction process correspond to hemes I and IV in the crystal structure.

Cytochrome c Group↗
PubMed1987

Neurofibrillary tangles in association with congenital hydrocephalus.

Morphologic study of the brain from a retarded patient with progressive congenital hydrocephalus revealed widespread neurofibrillary tangles in the cerebral cortex and the brain stem. Senile plaques were not found. The tangles consisted of paired helical filaments. Scanning electron microscopic energy spectrometric analysis failed to demonstrate abnormal accumulation of aluminum or other elements in the involved neurons.For the first time the association of congenital hydrocephalus and neurofibrillary tangles is reported. This observation is consistent with the hypothesis of interference with axonal transport of neurofilaments as a common pathogenetic mechanism in the genesis of neurofibrillary tangles in human brains.

Adult↗
PubMed1986

Cerebral sparganosis.

Cerebral sparganosis is caused by the migrating larva of Spirometra mansonoides. Only seven cases have been reported worldwide. We here report the second known case in the United States. Including our case, ages ranged from 24 to 46 years. Men and women were equally affected. Headache, convulsions, focal neurologic signs, and peripheral eosinophilia were common. CT often revealed an enhancing mass. Surgical resection of the parasitic granuloma gave excellent results. often revealed an enhancing mass. Surgical resection of the parasitic granuloma gave excellent results.

Adult↗
PubMed1985

Immunoperoxidase study of primary central nervous system lymphomas.

Primary central nervous system (CNS) lymphomas have been perceived as CNS counterparts of systemic non-Hodgkin's lymphomas (NHL). Their pathogenesis in respect to the cell of origin, however, has been controversial. A highly sensitive and specific immunoperoxidase method for cytoplasmic immunoglobulins (CIg) using anti-kappa and anti-lambda light-chain antisera in addition to antibodies against IgM, IgG, IgA and IgE heavy chains and J-chain was performed on 27 surgically removed and histologically confirmed primary CNS lymphomas. In order to increase the sensitivity, slides were treated with trypsin to expose the various CIg components. Results indicated that the majority of CNS lymphomas (20 cases or 74.01 percent) were negative for monoclonal CIg. Only four cases (14.81 percent) were definitely positive for CIg with monoclonal staining pattern. Results of the remaining three cases were inconclusive. Among those four cases with positive CIg, three were histologically identified as immunoblastic sarcomas according to the Luke-Collins classification. It is concluded that, in contrast to systemic NHL, primary CNS lymphomas are mostly negative for monoclonal CIg. Whether these CIg negative neoplasms are T and/or null cells in nature or whether they represent an unidentified group of neoplasms is not clear at the present.

Adult↗
PubMed1984

Intraoperative radiotherapy for intracranial malignancies. A pilot study.

Intraoperative radiotherapy (IOR) or "direct view" irradiation permits the delivery of a single exposure of high-energy electrons to a surgically exposed tumor. Surgical exposure permits physical retraction of normal uninvolved tissues away from the IOR beam as well as the accurate assessment of the target volume. IOR represents a "supplement" or "boost" dose to conventional fractionated external beam irradiation that is administered postoperatively. This pilot study represents the clinical experience in the US using IOR for brain tumors. At Howard University Hospital, Washington, DC, 12 patients underwent surgical resection or decompression and 1500 cGy were delivered to the tumor bed intraoperatively. After surgical recovery, 5000 cGy in 25 fractions were delivered to the whole brain and an additional 500 cGy cone-down boost were delivered to the tumor bed. This protocol was best tolerated when the cranial vault was decompressed. Two patients with meningioma are without evidence apparently NED at 8, 11, 12, and 15 months, respectively. A fifth patient died at 8 months NED from an accident. Three glioma patients died with disease at 3, 13, and 15 months, respectively. Two additional patients died 30 days after surgery. Indications, techniques, and clinical findings are presented.

Adolescent↗
PubMed1983

Pineal calcification among black patients.

A postmortem histopathological study was done in 233 pineal glands of black patients. Among them, 70 percent showed microscopic evidence of calcification in the pineal parenchyma. The frequency of calcification increased with age. However, the severity of calcification reached the peak in the 60 to 69 year old age group and then gradually declined. As compared to males, females had slightly higher frequency and reached the peak of severity in younger age groups. When pineal calcification was compared among patients with various malignancies, a higher frequency and more severe calcification were observed in patients with carcinoma of the prostate and the pancreas. A lower frequency and less severe calcification were observed in patients with carcinoma of the breast and the cervix. The results of this study emphasize the important role of sex hormone in genesis of pineal calcification.

Adolescent↗
PubMed1982

Disseminated intravascular coagulation involving the brain: a topographical study.

Histopathological study on 723 brains from routine necropsies was performed. Ten brains (1.38 percent) were found to have histological lesions of disseminated intravascular coagulation (DIC) with multiple fresh fibrin and/or platelet thrombi in the cerebral microcirculation. Among them, premortem diagnosis was made in only one case, and only two cases also showed evidence of visceral involvement. Microthrombi were found most frequently in the cerebral cortex and hypothalamic region and in the cerebral white matter, brain stem, and cerebellum, in descending order. Neurological symptoms and signs, including lethargy, coma and seizure, were detected in all cases. The abnormal body temperature and/or urinary output observed in most patients appeared to be related to the frequent hypothalamic involvement by DIC. The exclusive or predominant involvement of the brain by multiple microthrombi may be considered as a localized form of DIC. It is probably related to cerebral ischemia since severe acute neuronal ischemic changes also were noted in most brains.

Adult↗
PubMed1981

Spinocerebellar degeneration with parkinsonian features: a clinical and pathological report.

A 20-year-old patient had spinocerebellar degeneration and parkinsonian tremor that improved with L-dopa treatment. Postmortem examination revealed posterior column atrophy in the spinal cord and severe degeneration in the substantia nigra. Atrophic changes were noted in deep cerebellar nuclei and superior cerebellar peduncles. This study confirms the relationships between clinical parkinsonism, substantia nigra atrophy, and the therapeutic effect of L-dopa.

Adult↗
PubMed1979

Metastatic brain tumors in two predominantly black hospitals: a statistical analysis.

A retrospective statistical analysis was done on metastatic brain tumors collected from two predominantly black hospitals in Washington, DC. A composite African series of metastatic brain tumors was also constructed for comparison. The results indicate that bronchogenic carcinoma is the predominant metastatic brain tumor (45.2 percent) among American blacks in Washington, DC, and chorioepithelioma, the most common (20.0 percent) among African blacks. In comparing these two series, much dissimilarity in the pattern of tumor distribution between these two genetically related ethnic groups suggests an important environmental role in the genesis of metastatic brain tumors.The present study also reveals a relatively high proportional frequency of prostatic carcinoma among metastatic brain tumors in blacks (3.8 percent in Washington, DC, and 2.1 percent in Africa).

Adolescent↗
PubMed1978

Melanosis of the dentate nucleus: fine structure and histochemistry.

Ultrastructural and histochemical studies were done on a rare case of primary melanosis of the dentate nucleus. The coexistence of extraneuronal neuromelanin and glial lipofuscin in that region was observed and the interconvertability of these two pigments is suggested.

Aged↗
PubMed1977

The ethnic distribution of primary central nervous system tumors: AFIP, 1958 to 1970.

A retrospective ethnic study was made of 16,311 cases of primary central nervous system (CNS) tumors seen at the Armed Forces Institute of Pathology (AFIP), Washington, D.C., from 1958 to 1970. Results showed a considerably higher Caucasian:Negro (C:N) case ratio (13.7:1) than the C:N population ratio (8.4:1), indicating a higher relative frequency of primary CNS tumors in American Caucasians as compared to American Negroes. The glioma was significantly more frequent in Caucasians than in Negroes (p less than 0.005). In contrast, Negroes had an excess of the pituitary adenoma as compared to Caucasians (P less than 0.01). The proportional frequencies of the meningioma and the nerve sheath tumor were also higher in Negroes than in Caucasians. When this pattern of the tumor distribution of American Negroes was compared to that of African Negroes (a composite African series), the preponderance of the pituitary adenoma and the meningioma and the relative paucity of the glioma in the Negro race as compared to Caucasians were again confirmed. The differences in the relative frequency and the tumor distribution between American Negroes and Caucasians and the considerable similarity of the tumor distribution between American and African Negroes emphasize the importance of genetic factors in the development of at least some primary CNS tumors.

Adolescent↗
PubMed1976

Neoplasms of the central nervous system. incidence and population selectivity in the Washington DC, metropolitan area.

During the period 1960 through 1969, 990 primary neoplasms of the central nervous system were diagnosed in hospitals in the Washington, DC, Standard Metropolitan Statistical Area (SMSA). All cases were identified according to age, race, sex, histologic type, and date of diagnosis. A West African composite of 253 cases was used for comparison. In the Washington SMSA, the age-adjusted incidence rates were: for Caucasians 5.5 in males and 3.6 in females and for Negroes 4.8 in males and 3.4 in females per 100,000 annual population. Caucasians in the Washington SMSA had a higher relative proportion of gliomas than Negroes in the same area and in Africa (p less than 0.005). The relative proportion of pituitary adenomas was higher in American Negroes (p less than 0.005) and in Africans than in Caucasians. The comparable pattern of CNS tumors in American and African Negroes, relative to Caucasians, suggests that in the development of neoplasms of the central nervous system racial factors may be of importance.

Africa, Western↗