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Biomedical subjects

P Johnson

Publications and source records attributed to P Johnson.

At least 523 records · Page 29Linked to original sources
PubMed1981

Effects induced by two different estrogens on serum individual phospholipids and serum lecithin fatty acid composition.

Eleven oophorectomized women (mean age 34.5 +/- 5.9) received two treatment cycles, one of the 17-C-alkylated ethinyl estradiol 20 microgram per day, and the second of the non-alkylated estrogen, estradiol valerate 2 mg per day for six weeks in separate periods preceded by six weeks without hormonal replacement therapy. Blood samples were drawn before and after six weeks on each estrogen. The samples were assayed for individual phospholipids i.e. cephalin, lecithin, lysolecithin and sphingomyelin after separation of these lipids by thin layer chromatography. The relative fatty acid composition of serum and high density lipoprotein lecithin and serum cholesterol ester was determined by gas liquid chromatography. Both estrogens reversed the symptoms of estrogen deficiency and had similar effects on serum individual phospholipids i.e. causing an increase in lecithin concomitant with a decrease in lysolecithin. It is suggested that this lecithin-lysolecithin shift could depend on an inhibition of the hepatic lipase and its phospholipase A1-activity. Both estrogens increased serum lecithin arachidonic acid without causing any change in linoleic acid (the major essential fatty acid), which indicates that this increase in arachidonic acid could be an estrogenic effect independent of dietary factors. Ethinyl estradiol caused an increase in palmitic and a decrease in stearic acid in the 1-position of serum lecithin while estradiol valerate did not influence these fatty acids at all. This palmitic-stearic acid shift induced by ethinyl estradiol is interpreted as a non-hormonal "drug-effect" linked to the liver toxicity of 17-C-alkylated steroids in spite of the lack of influence on routine liver function tests.

Adult↗
PubMed1981

Serum-mediated adherence of feline granulocytes to microfilariae of Brugia pahangi in vitro: variations with parasite maturation.

Feline eosinophils and neutrophils readily adhered in vitro to the sheaths of microfilariae of Brugia pahangi in the presence of suitable serum. Both cell types flattened along the surface of the parasite undergoing cytoplasmic changes which included degranulation. Adherence was dependent on properties of both the serum and the history of the microfilaria used. Two types of serum factor were found to mediate adherence. Heat labile factors were present in sera from infected and uninfected cats as well as in sera from other species. They were removed by preincubation of sera with zymosan suggesting that complement components were involved. This suggestion was supported by the demonstration of C3 on the surface of microfilariae participating in adherence reactions. A heat stable factor, present in the serum of less than 10% of infected cats, also mediated adherence. This factor was demonstrated to be IgG by immunoadsorption and immunofluorescence. The ability of the microfilariae to participate in the adherence reaction mediated by complement factor varied with maturation of the parasite. Microfilariae obtained directly from the uteri of adult worms, or produced in vitro, did not possess the ability to participate in adherence. Young blood microfilariae (i.e. taken from the blood of cats recently patent) were similar to the in vitro produced parasites; however, the majority of blood microfilariae from infections of greater than three weeks patency participated in this form of adherence. No difference between blood and uterine/in vitro microfilariae was seen in adherence reactions mediated by heat stable antibody.

Animals↗
PubMed1981

A negative serological relationship between cases of grass sickness in Scotland and Clostridium perfringens type A enterotoxin.

In an attempt to compare the equine grass sickness as reported in Europe with that described in the Republic of Colombia, sera from horses experiencing grass sickness in Scotland were used in neutralisation tests with Clostridium perfringens type A enterotoxin. The sera, from acute and chronic cases of the disease, failed to neutralise either crude or partially-purified enterotoxin. Neither were precipitin lines formed when the sera were treated against the toxin in immunoelectrophoresis. These results suggest that grass sickness in Europe and the equine disease in Colombia have a different aetiology.

Animals↗
PubMed1981

Evaluation of the polyethylene glycol precipitation method for the estimation of high-density lipoprotein cholesterol.

Treatment of fresh sera with polyethylene glycol 6000 at a final concentration of 100 g/l produced selective precipitation of low-density lipoproteins with only traces of contamination with high-density lipoproteins, as determined by electroimmunoassay using antisera to human alpha1-lipoprotein and human beta-lipoprotein. Supernatants collected for high-density lipoprotein-cholesterol estimation were free from low-density lipoproteins. Precipitates sedimented readily from specimens with high triglyceride contents, and secondary precipitation during enzymatic cholesterol determinations was absent. Values obtained by this method correlated well with those obtained by precipitation of low-density lipoproteins with heparin and manganous ions at concentrations optimal for discrete of lipoprotein classes (r = 0.975; p less than 0.001).

Chemical Precipitation↗
PubMed1981

Loss of A-apoprotein immunoreactivity during high-density lipoprotein separation.

By use of an electroimmunoassay, concentrations of A-apoproteins were estimated in serum and in corresponding apoprotein fractions isolated by ultracentrifugation. These values were compared with high-density lipoprotein concentrations determined by analytical ultracentrifugation. Concentrations of A-apoproteins estimated in serum were considerably higher than in isolated high-density lipoprotein fractions. These discrepancies could not be accounted for entirely by material losses into other fractions during ultracentrifugal fractionation. No comparable differences in apoprotein-B concentrations were observed during the ultracentrifugal separation of low-density lipoprotein. Concentrations of A-apoproteins estimated in the residual serum after precipitation of low-density lipoproteins by heparin and manganous ions were also lower than in the corresponding whole sera. The discrepancies persisted after treatment of serum and isolated fractions with tetramethylurea, urea (9 mol/l), and by heating at 52 degrees C for 3 hours. It is considered that separation by ultracentrifugation induces subtle alterations in the surface structure of the lipoprotein species which give rise to changes in immunoreactivity.

Antigens↗
PubMed1981

Treatment with oral estrone sulphate in the female climacteric. I. Influence on lipids.

Twenty women in the perimenopause were studied for 12 months during which sodium-piperazine-estrone-sulphate 2.5 mg/day was given for 3 weeks out of 4 as a hormone replacement therapy. Blood samples were drawn at the start of therapy, then after 3, 6 and 12 months and analyzed for serum triglyceride, total cholesterol, cholesterol content of high density lipoprotein (HDL) fraction and the relative fatty acid composition of serum lecithin. Triglyceride levels were increased after 3 months (p less than 0.01). After that there was a gradual decline to almost pretreatment levels. Total cholesterol decreased during the latter period of treatment and became virtually normal; significantly lower levels (p less than 0.01) were found at 12 months. The HDL-cholesterol, which constitutes most of the high density lipoprotein fraction, showed a continuous increase and reached statistical significance at 12 months (p less than 0.01). This type of lipoprotein pattern is associated with a reduced risk of ischemic cardiovascular disease. After 3 and 6 months of treatment an increase in the relative content of palmitic acid in serum lecithin was seen, an increase that might indicate an altered liver lecithin synthesis, usually seen in cholestasis. However, after 12 months the palmitic acid level declined and was not significantly altered from the pretreatment value, indicating that the change was transitory.

Adult↗
PubMed1981

Substances derived from 4-de-N-methylfortimicin B.

The preparation of 4-de-N-methylfortimicin A analogs as well as the preparation of 4-de-N-methyl-4-N-(beta-aminoethyl)-4-N-ethylfortimicin B is reported. It was shown that the 4-N-methyl group in fortimicin analogs is essential for antibacterial activity since neither the 4-de-N-methylfortimicin A nor the 4-de-N-methyl-4-N-(beta-aminoethyl)-4-N-ethylfortimicin B exhibited useful biological activity.

Aminoglycosides↗
PubMed1981

Oxygen and carbon dioxide tensions, breathing and heart rate in normal infants during the first six months of life.

Daytime measurements were made of the relationship between sleep state, cardio-respiratory changes and oxygen (transcutaneous PO2) and carbon dioxide (mass spectrometer alveolar PCO2) tensions in eleven normal infants from birth to 6 months of age. Sequential records were made at 1 week, 1, 3 and 6 months. The babies were not restrained, slept in a cot, and were constantly observed. Heart rate was higher in active sleep than in quiet sleep at all ages and rose between 1 week and 1 month (P less than 0.01) in both quiet sleep and active sleep and then decreased at 3 and 6 months. Respiratory rate only changes with age in active sleep at 6 months, showing a decrease (P less than 0.05) but was higher in active sleep that in quiet sleep at 1 month (P less than 0.002) and 3 months (P less than 0.02). A fall in heart rate (less than 100 beats/min) occurred chiefly in association with apnoea. The incidence of apnoea (of greater than 3 s duration) varied widely between babies at the same age and in the same baby at different ages but was most common in the first 3 months of life. No evidence of obstructive apnoea was found and no apnoea of greater than 12 s duration was observed. Period breathing occurred in all babies at 1 month normally following sighs but was uncommon at 1 week and 3 months and absent at 6 months. A fall in transcutaneous PO2 did not precede but often resulted from an episode of periodic breathing.

Aging↗
PubMed1981

Absorption and disposition of [14C]-molsidomine in laboratory animals.

14C-Labelled N-ethoxycarbonyl-3-morpholinosyndnonomine(14C-molsidomine, Corvaton) was administered orally to mouse, rat, rabbit, dog and rhesus monkey, and i.v. to rat and dog, at a dose level of 6 mg/kg-1. The rates and routes of excretion of radioactivity were determined. The oral dose was well-absorbed in all species and most (greater than 75%) of the radioactive dose was excreted in urine. In rat and dog less than 1% of the dose was present as expired 14CO2. In dog and rhesus monkey, small amounts of radioactivity were eliminated relatively slowly. In rat, dog and rhesus monkey, the three species examined in detail, radioactivity was generally distributed throughout the body 4-10 days after dosing. Levels were highest in liver, pelt, blood and the gastrointestinal tract. Whole-body autoradiographic studies in rat and rhesus monkey showed that at 4 days post-dose, radioactivity was highest in stomach wall and was distributed into other tissues in lesser amounts. In view of its mode of action, it was interesting that radioactivity was also associated with the heart muscle and aorta walls.

Animals↗
PubMed1981

Effect of histamine and prostaglandin E2 on gastric blood flow in swine.

Gastric blood flow was measured by the radioactive microspheres entrapment technique following the IV infusions of saline solution, histamine, or prostaglandin E2 and histamine to young pigs. Pigs treated with histamine (2 micrograms/kg/minute for 60 minutes) had significantly higher blood flow to the gastric mucosa (P less than 0.025), particularly to the region of the proper gastric (fundic) glands (P less than 0.01), than did the saline-treated pigs. When prostaglandin E2 (1 microgram/kg/minute for 60 minutes) was infused simultaneously with histamine, there was a slight, but not significant, decrease (P less than 0.10) in mucosal blood flow to the region of the proper gastric glands. Analysis of the percentage distribution of blood flow indicated that the increase in blood flow to the region of the proper gastric glands after histamine infusion may be due to a redistribution of blood flow from the cardiac gland region.

Animals↗
PubMed1981

Effects of bone wax on bacterial clearance.

The hemostatic benefit of bone wax placed in cancellous bone occurs at the expense of the wax persisting at the bony site for years. As such, bone wax appears to act as a foreign body. This study examines the effect of bone wax on the ability of cancellous bone to clear bacteria. The iliac crest of rabbits was penetrated to a standard depth with an 18-gauge needle. Subsequently, nothing or Staphylococcus aureus, 10(5) colony-forming units, was innoculated in the needle site and followed by the subcortical placement of a cylinder of bone wax or similarly sized stainless steel rod. Ten days later, the site of bony penetration was excised and cultured. Eighty percent of animals whose bone was implanted with bacteria and bone wax together had positive cultures. Forty percent of animals whose bone was implanted with bacteria and a steel rod also had positive cultures. The difference between these groups (bacteria with bone wax or with steel rod) was not statistically significant. However, these combinations of bacteria with foreign body were significantly different from the bacteria only or bone wax only or steel rod only groups in which no positive cultures were observed. The data indicate that bone wax significantly impairs the ability of cancellous bone of rabbits to clear a standard inoculum of S. aureus. This effect appears to be the same as that observed with a different but similarly sized foreign body (steel rod).

Animals↗
PubMed1980

Selective degeneration of interneurons in the motor cortex of infant monkeys following controlled hypoxia: a possible cause of epilepsy.

Infant monkeys have been subjected to hypoxia with an arterial pO2 of 20-22 Torr for 30 min. Following perfusion 1-2 weeks later electron microscopy of the motor cortex shows a selective degeneration of axon terminals making symmetrical synapses and which probably arise from inhibitory GABAergic interneurons. It is suggested that this may be related to the development of epilepsy following hypoxia.

Animals↗
PubMed1980

Intermediate filaments of bovine pulmonary artery smooth muscle distribution, isolation and polypeptide composition.

1. The distribution of intermediate filaments in bovine pulmonary artery smooth muscle was studied. 2. These filaments contained at least two polypeptides of 43,000 and 55,000 daltons. 3. The 55,000 dalton polypeptide was purified by ion-exchange chromatography. 4. The amino acid compositions of the polypeptides were determined. 5. The 55,000 dalton polypeptide and a mixture of the 43,000 and 55,000 dalton polypeptide reassembled into structures similar to native intermediate filaments.

Amino Acids↗
PubMed1980

Respiratory function of the larynx in developing sheep and the influence of sleep state.

The activities of laryngeal abductor and adductor muscles were recorded in conjunction with other respiratory muscles in unanaesthetized chronically monitored foetal, newborn and adult sheep. In foetuses, rhythmical breathing movements occurred in the presence of rapid eye movements and a low voltage electrocorticogram (REM state) and were accompanied by phasic laryngeal abduction; adductor muscles and intercostals were largely inactive. During the foetal non-REM state laryngeal adductor muscles were tonically active at a low level, but the glottis remained open. Deep inspiratory efforts which occurred at low frequency in this behavioural state were not accompanied by abductor activity and resembled inspiratory efforts associated with regurgitation in ruminants. After birth, expiratory adductive activity of the larynx was also maximal during non-REM sleep and negligible during REM sleep. Active laryngeal adduction was accompanied by delayed expiratory airflow, prolonged TE and reduced respiratory frequency. Adduction of the larynx is dependent on behavioural state and appears to be the principal means of regulating TE in sheep, particularly during early post-natal development.

Action Potentials↗