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Biomedical subjects

G John

Publications and source records attributed to G John.

At least 55 records · Page 3Linked to original sources
PubMed1992

Calcium antagonists can be classified using in vitro toxicity and potency indices.

The toxicity of eleven calcium antagonists from different chemical families was determined in rat hepatocyte primary cultures. The calcium antagonist potency of the same compounds was also determined in isolated rabbit aortic rings contracted with high K+. The hepatocytotoxicity of the calcium antagonists was not directly linked to blockade of voltage-operated calcium channels, since there was no correlation between the rank order of hepatotoxicity and that for calcium antagonist potency. The toxicity and calcium antagonist potency of each calcium antagonist examined were used to calculate an in vitro therapeutic index value for each compound. It was observed that therapeutic indices fell into three distinct groups and we therefore propose that the in vitro therapeutic index can be used to subclassify the calcium antagonist group of drugs. The proposed classification corresponds very closely with one already suggested by Spedding on pharmacological grounds. In conclusion, the in vitro therapeutic index may provide a useful tool in the characterization and subclassification of novel calcium antagonist compounds.

Animals↗
PubMed1992

Combined trabeculectomy, cataract extraction, and foldable lens implantation.

The efficacy of foldable silicone intraocular lenses in combined glaucoma/cataract surgery was retrospectively analyzed in 19 consecutive operations. Preoperatively all patients were receiving medical treatment for glaucoma; 21% had intraocular pressures above 21 mm Hg despite the medical therapy. Postoperatively, reduction of intraocular pressure to 21 mm Hg or less was achieved in 84% of eyes, with 58% requiring no antiglaucoma medications. Mean improvement of Snellen visual acuity was 4.9 lines; 84% of eyes achieved a final acuity of 20/40 or better. Median follow-up was 59 weeks (range 25 to 88 weeks). Thirteen eyes (68%) had a filtration bleb present when last examined. These preliminary results suggest that foldable silicone IOLs are an effective alternative to poly(methyl methacrylate) lenses in combined glaucoma/cataract surgery.

Cataract Extraction↗
PubMed1992

Subconjunctival injection of purified blood mononuclear cells into alkali-injured rabbit eyes.

Monocytes transform into tissue macrophages that scavenge necrotic debris from wounds but also release substances stimulatory to fibroblasts. In an effort to encourage the healing process, monocytes, purified from rabbit blood, were injected subconjunctivally 1 or 2 days and 6 or 7 days after alkali injury to the rabbit eye. The injected monocytes failed to alter the course of the alkali-injured eyes. Specifically, the incidence of corneal ulceration in the experimental group was not statistically different from that of the control group. A byproduct of this study was a presentation of the technique to purify platelet-free mononuclear leukocytes from rabbit peripheral blood.

Animals↗
PubMed1990

Infective endocarditis due to Streptococcus sanguis I occurring on a normal mitral valve.

We report a 64 year old lady in whom infective endocarditis of the mitral valve occurred with no previous underlying heart disease. Streptococcus sanguis I was isolated on blood culture and 2-D echo cardiography showed a vegetation on the anterior mitral leaflet. The viridans group of streptococci are classically associated with subacute endocarditis occurring on structurally abnormal valves, but involvement of a normal valve by these organisms is rare.

Echocardiography↗
PubMed1989

Predicting who will use a hearing aid.

Elderly patients receiving a hearing aid have usually experienced a hearing disability for many years. Simple methods of screening the pre-retirement age group for hearing impairment are described. Screening is feasible and effective.

Aged↗
PubMed1989

Clinical profile of Indian non-insulin-dependent diabetics with nephropathy and renal failure.

We studied the clinical profile of 296 non-insulin-dependent diabetic (NIDDM) patients with nephropathy and renal failure. Male preponderance was striking in this group and the age of onset of diabetes was between 30 and 50 years in 75%. Retinopathy was present in 86% with proliferative changes in 20% and coronary artery disease was evident in 40% of the patients. The incidence of retinopathy and coronary artery disease was significantly higher in this group than in a group of non-insulin-dependent diabetics without nephropathy (86% vs. 18.5%; 40% vs. 30% respectively, P less than 0.01). It is our observation that patients with NIDDM developing nephropathy and renal failure have had an early onset of disease and are significantly more often male. There is also a greater incidence of elevated blood pressure, coronary artery disease and retinopathy in this group.

Adult↗
PubMed1988

Ocular lawnmower injuries.

In the 10-year period from 1977 to 1987, lawnmowers have been responsible for approximately 70,000 injuries annually with an estimated 5% (3300) involving the eyes. Hyphema, angle recession, and traumatic retinopathy are especially common forms of lawnmower ocular trauma. A series of 14 cases of lawnmower-induced eye injuries is presented along with demographics of the patient population involved. An analysis of various types of lawnmowers currently in use are also included, and preventive measures are suggested.

Accidents, Home↗
PubMed1988

Field evaluation of polycarbonate versus conventional safety glasses.

Of all the causes of eye injury, gunshot has recently been cited as resulting in the highest rate of blindness and the lowest rate of visual recovery. Many of these cases are hunting accidents in which safety glasses could have prevented or lessened ocular damage. To evaluate the effectiveness of various types of safety glasses, we fired a Remington automatic shotgun at mannequin heads fitted with one of four types of safety lenses. From a distance of 10 yards, only polycarbonate lenses provided even partial protection. At 30 yards, polycarbonate and heat-treated lenses provided the best protection, whereas chemically treated and CR39 lenses provided significantly less protection. We recommend that hunters using shotguns in areas of poor visibility wear widely available polycarbonate safety glasses as well as "hunter's orange" to minimize their risk of devastating ocular gunshot injury.

Accidents↗
PubMed1986

Chronic valproic acid and coantiepileptic drug therapy and incidence of increases in serum liver enzymes.

Results are described on the association of increased serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) activities with valproic acid (VPA) and coantiepileptic drug therapy in a group (n = 126) of randomly selected chronically medicated out-patients. The highest incidence (SGOT, 28.3%; SGPT, 26.1%) of elevations occurred in patients comedicated with VPA-phenobarbital (PB)-phenytoin (PHT) combinations, followed by those in the VPA-PB group (SGOT, 19.5%; SGPT, 7.3%). No SGPT elevations were detected in any patients (n = 40) on chronic VPA monotherapy, while SGOT was marginally elevated in 20% of the cases. Considering the total sample (n = 126), SGOT activities were found to be linearly and directly correlated with VPA plasma concentration (n = 126, r = 0.228, p less than 0.01), PB concentration (n = 86, r = 0.352, p less than 0.01), PHT concentration (n = 45, r = 0.336, p less than 0.01), sum of VPA-PB concentrations (n = 86, r = 0.440, p less than 0.001), and sum of VPA-PB-PHT concentrations (n = 45, r = 0.481, p less than 0.001). The corresponding correlations for SGPT activities were similar, except that no correlation was observed in the case of VPA monotherapy. Student's t tests for equality of means showed that the subgroup with abnormal enzyme activities had a significantly higher mean plasma concentration for PB, PHT, sum of VPA-PB, and sum of VPA-PB-PHT when compared with normal enzyme subgroup patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Chronic valproic acid therapy and incidence of increases in venous plasma ammonia.

Results are described on the association of elevated ammonia (NH3) with valproic acid (VPA) therapy in a large group (n = 157) of randomly selected, chronically medicated (greater than 2 years) outpatients. The highest incidence (45.5%) of elevations occurred in patients comedicated with VPA-phenobarbital (PB)-phenytoin (PHT) combinations, followed by VPA-PB (33.3%) and VPA-PHT (15.4%). No NH3 elevations were detected in all patients (n = 38) on chronic VPA monotherapy. Considering the total sample (n = 157), NH3 concentrations were found to be linearly and directly correlated with VPA plasma concentration (n = 125, r = 0.249, p less than 0.001), PB concentration (n = 86, r = 0.411, p less than 0.001), sum of VPA-PB concentration (n = 60, r = 0.721, p less than 0.001), and sum of VPA-PB-PHT concentration (n = 33, r = 0.802, p less than 0.001). When patients in the subgroups (n = 73) that included all the patients with elevated NH3 were separated into one group (n = 47) with normal NH3 (less than or equal to 0.70 micrograms/ml) and one group (n = 26) with elevated NH3 (greater than or equal to 0.71 micrograms/ml), Student's t tests for equality of means showed that the group with elevated NH3 had a significantly higher mean plasma concentration for VPA, PB, sum of VPA-PB, and sum of VPA-PB-PHT (all at p less than 0.001) when compared with the normal group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗