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Biomedical subjects

A Hamid

Publications and source records attributed to A Hamid.

At least 37 records · Page 2Linked to original sources
PubMed1997

Diffusion of resin monomers through human carious dentin in vitro.

The diffusion of 2-hydroxyethylmethacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light cured bonding resin-composite resin restorations through human carious dentin was investigated. Extracted human molar teeth with different degrees of caries were obtained from consenting donors. Teeth were classified into three groups according to caries severity (mild, moderate and severe) using subjective criteria. The outer carious lesions were then removed guided by a proprietary caries detector dye. Teeth with exposure of the pulp space after caries removal were excluded from the study. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 ml distilled water. Each cavity was restored with a HEMA containing bonding resin then a TEGDMA-containing resin composite. Water samples were retrieved over a time course and analyzed by high performance liquid chromatography. There was great variation between teeth in HEMA and TEGDMA permeability. The cumulative amounts released were of similar magnitude to those observed in non-carious teeth for the mild and moderately-severe groups. However, the cumulative amounts released were markedly greater in severely carious teeth than in those with moderate or mild caries.

Adult↗
PubMed1996

Variation in phosphoric acid concentration and treatment time and HEMA diffusion through dentin.

PURPOSE: The effects of phosphoric acid concentration and time of dentin treatment on the movement of 2-hydroxyethylmethacrylate (HEMA) from a bonding resin-resin composite combination through dentin were investigated in vitro. MATERIALS AND METHODS: Freshly extracted human third molar teeth were divided into seven groups each of 10 teeth. A closed chamber was attached to the CEJ of each tooth to contain 1 ml distilled water. An occlusal cavity of 6 mm diameter and remaining dentin thickness of 1.0-1.5 mm was prepared in each tooth. Dentin was treated with either 10% phosphoric acid for 15, 30 or 60 seconds or with 37% phosphoric acid for 15, 30 or 60 seconds. A control group not treated with acid was also prepared. The cavities were rinsed, dried and then treated with the HEMA-containing Scotchbond Multi-Purpose bonding resin which was light-cured for 10 seconds. The cavities were then restored with Z100 and light-cured for 30 seconds. Water samples were retrieved from the chambers over a time course (4.32, 14.4, 43.2, 144 & 432 minutes; 1, 3 and 10 days) and analyzed by high performance liquid chromatography. RESULTS: HEMA was detected in the pulp chambers of all teeth from 4.32 minutes after resin placement. Mean total (cumulative) release at 10 days for all groups was in the 2-4 mumol range. The highest HEMA diffusion rate was 4.32 minutes after placement and were in the range 6-13 times greater than control in the 10%-15 seconds, 10%-30 seconds, 10%-60 seconds, 37%-15 seconds, and 37%-30 seconds groups. Unexpectedly, by far the lowest early rate at 4.32 minutes was in the 37%-60 seconds group (0.6 times of no-acid control).

Acid Etching, Dental↗
PubMed1994

A preliminary chemotaxonomic review of Kopsia (Apocynaceae).

The present paper is the result of a botanical and chemical study of the Indo-Pacific genus Kopsia (Plumerioideae-Rauvolfieae) Apocynaceae. Some of the species of this genus possess medicinal uses. A survey of the accepted taxa and their synonymy, based on the study of types, is presented. Studies on alkaloids provides chemotaxonomic information. Indeed, in some cases, chemical relationships occur between species belonging to the same botanical group.

Alkaloids↗
PubMed1993

Flavonone and chalcone derivatives from Cryptocarya kurzii.

Four complex flavanones, kurziflavolactones A [2], B [3], C [4], and D [5] and a complex chalcone 6 with an unprecedented carbon side chain on the flavanone or chalcone A ring have been isolated from a Malaysian plant, Cryptocarya kurzii (Lauraceae). Their structures were determined by extensive spectroscopic analysis, especially 2D nmr experiments. Compounds 3 and 6 showed slight cytotoxicity against KB cells, with IC50 values of 4 and 15 micrograms/ml, respectively. A biosynthetic pathway for the formation of these compounds is suggested.

Antineoplastic Agents, Phytogenic↗
PubMed1991

Effect of supplementary feeding of pregnant women on birth weight of the new born.

A supplementary food mix was prepared from roasted peanut, chickpea and sugar. The effect of this food mix on birth weight was tested on a group of rural women of low socioeconomic group in few villages in Peshawar District of NWFP. A 100 g supplementary food mix providing 16.7 g protein and 520 K.Cal of energy was given daily to a group of mothers in their third trimester, until the time of delivery. Another group of pregnant women acted as control. The results indicaed a high maternal weight gain in the supplemented group. Moreover the birth weight, length, head and chest circumference of the new born in the supplemented group was also significantly higher as compared to control group.

Adult↗
PubMed1991

From Ganja to crack: Caribbean participation in the underground economy in Brooklyn, 1976-1986. Part 1. Establishment of the marijuana economy.

The involvement of Caribbean youth in drug distribution (marijuana from the mid-1960s to 1981; cocaine hydrochloride powder and crack from 1981 to 1987, the time of writing) throughout the Circum-Caribbean area and in North America is described. Social, economic, and cultural outcomes of these engagements are highlighted, and the relationship between the underground economy of drugs and the corporate, capitalist economy is explored. Responding to high rates of unemployment and to other problems of migrant adaptation, young Caribbean African males established a multimillion dollar marijuana (ganja) trading network which linked cultivators on the islands with exporters/importers and street-level distributors in North American cities. By 1976, its participants had become Rastafarians, or followers of an ideology of self-reliance and indigenous development. Following its precepts, they reinvested marijuana revenues to revive cottage industry and agriculture. In Caribbean or minority neighborhoods, therefore, marijuana was a "positive vibration" and its distributors were lionized.

Cannabis↗
PubMed1991

From Ganja to crack: Caribbean participation in the underground economy in Brooklyn, 1976-1986. Part 2. Establishment of the cocaine (and crack) economy.

Shortages in the supply of marijuana, which became acute around 1981, caused Rastafari marijuana distributors very reluctantly to disregard religious injunctions against the use of any psychoactive substance except marijuana, and to experiment with the use and distribution of cocaine hydrochloride powder for intranasal administration and, later, for smoking (freebase and crack). This experimentation proved ruinous, and many were retired ignominiously from drug distribution. In the crack era they have been succeeded by completely new social, cultural, and economic arrangements.

Cannabinoids↗
PubMed1991

Crack: new directions in drug research. Part 1. Differences between the marijuana economy and the cocaine/crack economy.

Crack use and trafficking in low-income, minority communities in New York City have pushed into prominence many aspects of drug use/misuse and distribution which had formerly received inadequate attention. For example, the generation and reinvestment of drug incomes are important determinants of how various drugs are experienced. While in retrospect marijuana trafficking appears to have been an almost benign affair, crack trafficking is fast-paced, ruthless, steeped in violence, and impoverishes everyone who becomes engaged in it. In this part the differences between rates, volumes, and methods of income generation related to the use and distribution of marijuana and cocaine are elaborated. The contrast raises a question: Do economies like drug distribution follow a particular rhythmic pattern (capital accumulation during the benign marijuana passage followed by capital depletion in the overheated crack era), and how is it related to the changing demands of the regional economy? Viewed from this perspective, drug distributors and users appear not so much as "deviant" or "alienated" or as a "reserve pool of labor," but rather as a type of labor force which does indispensable work for the whole society.

Cannabinoids↗
PubMed1991

Crack: new directions in drug research. Part 2. Factors determining the current functioning of the crack economy--a program for ethnographic research.

Factors which hypothetically influence rates, volumes, and methods of income generation in crack distribution, use, and misuse are indicated, and a research program to investigate them is suggested. This research will contribute significantly to the development of a theoretical framework which adequately relates substance using/abusing and trafficking populations to the wider community and will explain why crack use and distribution have had such different outcomes than marijuana. Factors to be researched include: polyethnicity, crack-related deculturation, gender differentiation in crack use and effects, neighborhood effects, vertically organized crack-distributing organizations, crack-related violence and crime, and replacement of previous drug markets by crack.

Crack Cocaine↗
PubMedDate not supplied

Further evidence for an exceptionally low prevalence of Helicobacter pylori infection among peptic ulcer patients in north-eastern peninsular Malaysia.

The Helicobacter pylori infection rate was determined in 124 consecutive patients with duodenal ulcers (DU), gastric ulcers (GU), duodenal erosions or gastric erosions diagnosed by endoscopy at a single institution in north-eastern peninsular Malaysia in 1996-97. Biopsies of the gastric antrum and body were subjected to the urease test, Gram staining of impression smears, culture and histopathological examination. Serology was undertaken on all patients using a locally validated commercial kit. Infection was defined as a positive result in at least one test. The infection rates were 20% (10/50), 21.2% (7/33), 16.7% (1/6) and 17.1% (6/35) in DU, GU, duodenal erosion and gastric erosion patients, respectively. The infection rate among Malays [7.0%, (6/86)] was lower than in non-Malays [47.4% (18/38)] (P < 0.001). There was a higher infection rate among males, who constituted 62.1% (77/124) of the sample. Seventy-eight patients (62.9%) were receiving non-steroidal anti-inflammatory drugs (NSAIDs) and 33 patients (26.6%) were neither receiving NSAIDs nor were infected with H. pylori. The H. pylori infection rate among peptic ulcer patients in this predominantly Malay rural population appears to be the lowest reported in the world thus far. Empirical H. pylori eradication therapy in peptic ulcer patients is clearly not indicated in this community. The possible reasons for the low prevalence of H. pylori infection are discussed.

Adult↗