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Biomedical subjects

K H Ng

Publications and source records attributed to K H Ng.

At least 19 recordsLinked to original sources
PubMed1992

Cloning of a human DNA sequence that restores expression of hepatic functions in a dedifferentiated rat hepatoma cell.

In a study of the regulation of gene expression in liver cells, a strain of dedifferentiated cells (C2) derived from the rat hepatoma line H4IIEC3 was transfected with DNA from human liver. After growth of these C2 variants in a glucose-free medium, revertants were selected which were characterized by the expression of a complete set of liver functions. A 4.3 kb human DNA sequence was detected with an Alu sequence probe in cells of four independent revertant clones and was shown to be an extrachromosomal, covalently closed duplex DNA. This molecule, called HALF1 for reversion inducing sequence, was cloned and transfected into C2 cells. Analyses of the transfectants indicated a correlation between the introduction of this cloned genomic human DNA sequence and the recovery of hepatic traits.

Adult↗
PubMed1992

Immunohistochemical study of the distribution of S-100 protein in pleomorphic adenomas of minor salivary glands.

Twelve pleomorphic adenomas of minor salivary gland origin were examined for the distribution of S-100 protein, detected using the peroxidase-antiperoxidase (PAP) method. Strong S-100 protein immunoreactivity was noted in areas containing plasmacytoid cells, stellate and spindle cells against a myxochondroid or hyalinous stroma, and solid epithelial areas. Tubular and duct-like structures showed variable stainability. Stromal tissue and normal salivary glands were generally negative for S-100 protein. These findings were compared with those reported elsewhere.

Adenoma, Pleomorphic↗
PubMed1992

Medical audit of hysterectomy in the Hunter Area of New South Wales.

A computer search in the New South Wales (NSW) Department of Health statistical data base was made to obtain the medical record numbers of patients who had had hysterectomies in the public or private hospitals of the Hunter Area of the State during the years 1987-89. The medical records of patients so identified were then extracted and reviewed by a medical team. The age at and the principal indication for hysterectomy were noted in each case and these data were then compared with those for the rest of NSW. The hysterectomy rate in the Hunter Area was 66.5 per 10,000 women aged 15 years or more, compared with a rate of 33.8 per 10,000 in the rest of NSW. When the 9.04% of hysterectomies performed on patients whose domicile was outside the Hunter Area were excluded, the corrected hysterectomy rate for the area was 57.46 per 10,000 women. The commonest indications for hysterectomy were menorrhagia (25.4%) and fibroids (15.32%). The limitations of this kind of retrospective study are discussed and suggestions are made for an improved methodology to be used in a future study.

Adolescent↗
PubMed1992

Immunolabelling of prolactin at ultrastructural level using the protein A-gold technique on Epon-embedded tissue.

The use of the colloidal-gold technique in electron microscopy immunocytochemistry has provided important information on the in situ localisation of intracellular antigens. We have developed a post-embedding technique for prolactin localisation on resin-embedded human pituitary tissue sections by the use of the protein-A gold conjugate. Human pituitary tissue obtained at autopsy was processed for electron microscopical study without post-osmication and then embedded in Epon. The indirect immunoperoxidase method was used for light microscopical targetting of lactotroph cells for subsequent electron microscopical antigen localisation. Ultra-thin sections were labelled with human anti-human prolactin followed by protein-A gold conjugate. Specific labelling was observed over secretory granules with a density of 15-30 particles per granule, as determined by the Quantimet 570 image analysis system. This technique provides a means of studying the pathophysiology of hormonal secretion at ultrastructural level and can be a useful tool in diagnostic and research investigations.

Epoxy Resins↗
PubMed1992

Denture hyperplasia and oncocytic metaplasia.

A case of denture hyperplasia of the upper labial sulcus with concomitant oncocytic metaplastic changes is described. The patient concerned is an elderly male wearing an ill-fitting upper full denture.

Aged↗
PubMed1992

Leiomyoma of the incisive papilla region: a case report.

Leiomyomas are benign neoplasms of smooth muscle origin. They represent rare entities in the oral cavity. A case arising from the incisive papilla region of a 3-month-old infant is described and the histogenesis as well as the biologic potential of this tumor are discussed.

Diagnosis, Differential↗
PubMed1991

Anti-implantation activity of S(-)- and R(+)-camphor-yuehchukene in rats.

(+/-)-Yuehchukene is a dimeric indole alkaloid with potent anti-implantation activity in rats. Since (+/-)-yuehchukene occurs in nature as a racemate, it would be desirable to find out which enantiometer is the bio-active form. To this end, S(-)-camphor-yuehchukene and R(+)-camphor-yuehchukene were synthesised and tested in three bioassay models. It was found that the R(+) enantiomer was the active form. It was equipotent with (+/-)-yuehchukene in both anti-implantation and estrogenic activity tests. It seems fair to conclude that both activities reside in the same molecule.

Alkaloids↗
PubMed1991

Comparison of bovine beta-casein hydrolysis by PI and PIII-type proteinases from Lactococcus lactis subsp. cremoris [corrected].

The action of the cell-wall-associated proteinases from Lactococcus lactis subsp. cremoris strains H2 and SK112 on bovine beta-casein was compared. The proteinase from the H2 strain was characterised as a PI-type proteinase since it did not hydrolyse alpha s1-casein and the initial trifluoroacetic acid-soluble products of beta-casein hydrolysis were identical to those previously identified as hydrolysis products of PI-type lactococcal proteinase action. The time-course of product formation by the proteinase from the H2 strain indicated that the bonds Tyr193-Gln194 and Gln182-Arg183 were the first to be hydrolysed. Cleavage of the bonds Gln175-Lys176, Ser168-Lys169, Ser166-Gln167 and Leu163-Ser164 was also very rapid. Four of the five bonds in beta-casein most susceptible to hydrolysis by the PIII-type proteinase from strain SK112 were different from those cleaved by the PI-type proteinase, initial hydrolysis being at the sites Tyr193-Gln194, Leu192-Tyr193, Asp43-Glu44, Gln46-Asp47 and Phe52-Ala53. Early hydrolysis at the three sites in the N-terminal region of beta-casein, leading to cleavage of the N-terminal phosphopeptide and rapid precipitation of the residual fragment, represents a marked contrast to the action of PI-type proteinases where cleavage at sites in the N-terminal region occurs only very slowly.

Amino Acid Sequence↗
PubMed1991

Nasofacial zygomycosis.

Zygomycosis is an uncommon polymorphic fungal disease. One clinical subtype, nasofacial zygomycosis, is caused by infectious exposure to the organism Conidiobolus coronatus. A case affecting the nose and lips of a 42-year-old Malay man is reported here. The clinicopathologic features and management of this disease are described, and its differential diagnosis is discussed.

Adult↗
PubMed1991

Plexiform granular cell odontogenic tumor: unicystic variant.

Plexiform granular cell odontogenic tumor of the mandible has recently been described. The cardinal histopathologic feature, as its name suggests, is a monophasic plexiform pattern of granular cells; the principal tumor in the differential diagnosis is granular cell ameloblastoma. Unlike the two previously reported cases of plexiform granular cell odontogenic tumor, which occurred as solid tumors in elderly men, the lesion reported here is a unicystic variant occurring in a middle-aged woman.

Cell Nucleus↗
PubMed1991

The combined epithelial odontogenic tumour in Malaysians.

The combined epithelial odontogenic tumour represents a hybrid lesion comprising primarily areas of adenomatoid odontogenic tumour intermixed with foci of calcifying epithelial odontogenic tumour. Five such cases retrieved from the files of the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, and four others from the existing literature were analysed. A mean age of 18.8 years, a female preponderance (66.7%) with a male to female ratio of 1:2 and predilection for the mandible (55.6%) were observed. All cases were treated by conservative surgery and the lack of recurrence confirmed the innocuous nature of this lesion.

Adolescent↗
PubMed1991

A prospective study of 245 open digital fractures of the hand.

We report a prospective study of 245 open digital fractures of the hand in 201 patients. Management followed clear guidelines set out in protocol. The incidence of infection (2.04%) and non-union (2.45%) was low. Proximal phalangeal fractures and comminuted fractures did worst and associated significant soft tissue injuries had a particularly deleterious effect on the outcome. A classification based on the different soft-tissue components involved is proposed. In fractures associated with simple lacerations or isolated digital nerve injury only, one can expect about 40% good results and about 25% poor results. Where extensor tendon injury or extensive skin loss are also present, there will be approximately 18% good results and 50% poor results. If there is also injury to the flexor tendon or more than one component of significant soft-tissue damage, about 80% will be poor and good results are rare.

Adolescent↗
PubMed1991

Calcifying and keratinizing ameloblastoma of the maxilla.

A case is described of ameloblastoma of maxilla presenting with numerous calcified keratin pearls. The significance of cellular variation in relation to the behavioural potential of the ameloblastoma in general is briefly discussed.

Adult↗
PubMed1991

Kimura's disease: a case report.

The clinical and histologic features of Kimura's disease are briefly outlined. A case presenting as a subcutaneous nodule in the region of the angle of the right mandible of a 20-year-old male is presented. The relationship of this disease to angiolymphoid hyperplasia with eosinophilia is discussed.

Adult↗
PubMed1991

Microwave ovens: mapping the electrical field distribution.

Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.

Electricity↗
PubMed1990

Peripheral ameloblastoma with clear cell differentiation.

This report details a case of mandibular peripheral ameloblastoma having a clear cell component. The latter consisted of ovoid cells with vacuolated or clear cytoplasm and vesicular or pyknotic nuclei that may be disposed as discrete clusters or show direct transition from typical acanthomatous areas. Comparison of this lesion with other odontogenic and nonodontogenic tumors that contain clear cells is discussed in the context of the differential diagnosis.

Ameloblastoma↗