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Biomedical subjects

J M Richards

Publications and source records attributed to J M Richards.

At least 73 records · Page 4Linked to original sources
PubMed1984

Rectal insemination modifies immune responses in rabbits.

Weekly deposition of pooled rabbit semen into the rectum in healthy male rabbits resulted in the appearance of immune complexes and antibodies to sperm and to peripheral blood lymphocyte antigens. It also led to a decreased ability to mount a humoral immune response to T lymphocyte-dependent antigens, keyhole limpet hemocyanin, and sheep red blood cells. These findings suggest that repeated rectal deposition of semen may compromise some aspects of the immune system.

Animals↗
PubMed1984

Sequential 22-hour profiles of breathing patterns and heart rate in 110 full-term infants during their first 6 months of life.

Sequential recordings (total number 365, mean duration 22 hours) of ECG and abdominal wall movement were obtained from 110 full-term infants up to 6 months of age. The longest pause in breathing movement per recording (maximum 21.6 seconds) decreased in duration over the first 2 weeks of life (P less than .005). Pauses greater than 18.0 seconds were not detected after seven days. The spread of values for pauses greater than or equal to 3.6 seconds duration was widest during the first 2 weeks, and their number decreased with age (P less than .001). Periodic breathing, detected in 69% to 80% of infants in all age groups, showed decreasing trends with age in total duration and maximum length of episode (P less than .005 for both). The spread of values was widest during the first 2 weeks (range for total duration 0 to 4.7 hours) and decreased with age. The mean respiratory rate during regular breathing decreased after 4 weeks (P less than .001). The spread of values was widest during the first 2 weeks and decreased with age. Birth weight was positively correlated with mean respiratory rate during the first three days of life (r = +.64, P less than .001). The mean heart rate during regular breathing increased during the first 15 days (P less than .001) and then decreased after 4 weeks (P less than .001). Higher mean heart rates were found in male infants (P less than .01).

Abdominal Muscles↗
PubMed1984

Non-immune IgG binding to the surface of spermatozoa by disulphide rearrangement.

The mechanism whereby immunoglobulin binds to the surface of spermatozoa was investigated. IgG reacts with spermatozoa non-specifically via the Fc portion of the molecule, while both IgM and IgA are completely unreactive. This selective binding of IgG is non-competitive, resistant to heat, proteases and non-ionic detergents and is not mediated by an Fc receptor on the sperm surface. Instead, evidence is presented that IgG covalently binds to spermatozoa by an exchange reaction between labile disulphides on both the sperm surface and IgG-Fc. It is calculated that there are 3 X 10(11) exchangeable disulphide bonds per bull spermatozoon.

Animals↗
PubMed1983

Influence of epididymal maturation on the capacity of hamster and rabbit spermatozoa for complement activation.

Hamster and rabbit spermatozoa released from the epididymis were tested for the ability to activate complement via the alternative pathway. While hamster spermatozoa were more active, the spermatozoa of both species reduced complement activity in homologous and also human serum previously adsorbed to remove sperm antibodies, and they bound C3 in the presence of EGTA + Mg2+. Hamster spermatozoa from the caput epididymidis were more anticomplementary and bound more C3 than did cauda spermatozoa and, though less marked, a similar difference was evident between caput and cauda spermatozoa from the rabbit epididymis.

Animals↗
PubMed1983

Induction of antibody to asialo GM1 by spermatozoa and its occurrence in the sera of homosexual men with the acquired immune deficiency syndrome (AIDS).

Compared to healthy homosexual and heterosexual men, homosexual men with acquired immune deficiency syndrome (AIDS) possessed significantly higher levels of IgG antibody to the neutral glycolipid asialo GM1 (ganglio-N-tetraosylceramide) (P less than 0.01). Of 31 homosexuals with AIDS, 36% possessed levels of this antibody that were at least two standard deviations above the mean of the healthy men. Furthermore, asialo GM1 antibody could be removed from serum by adsorption with spermatozoa. Weekly rectal insemination of male rabbits with rabbit semen also led to the appearance of antibody to asialo GM1 by 15 weeks. These results suggest that asialo GM1 is a component of ejaculated spermatozoa and demonstrate that rectal insemination by itself can lead to the production of antibodies to this glycolipid in the rabbit. In addition, asialo GM1 antibodies may be of value as a serological marker for the early detection of individuals with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Undetected episodes of prolonged apnea and severe bradycardia in preterm infants.

Twenty-four-hour tape recordings of ECG and breathing movement were made on 14 preterm infants with prolonged apneic episodes. Despite apnea monitoring systems, 136/203 (67%) apneic episodes greater than or equal to 20 seconds in duration, including 19 episodes greater than or equal to 50 seconds in duration, were not recorded by nursing staff. Of 120 apneic episodes greater than or equal to 30 seconds, 100 (89%) were accompanied by bradycardia less than or equal to 100 beats per minute. Episodes of more marked bradycardia (less than or equal to 80 beats per minute and up to seven minutes in duration) occurred without cessation of breathing movement in 10/14 infants studied. Treatment with theophylline or aminophylline was associated with a reduction in the number of episodes of apnea greater than or equal to 20 seconds accompanied by bradycardia less than or equal to 80 beats per minute (P less than .001). Many prolonged episodes of apnea and bradycardia are going unnoticed in neonatal intensive care units. Further studies are required to investigate and overcome the causes of these failures.

Aminophylline↗
PubMed1982

Prolonged apnea and cardiac arrhythmias in infants discharged from neonatal intensive care units: failure to predict an increased risk for sudden infant death syndrome.

Twenty-four hour recordings of respiratory wave form and ECG were made on low-birth-weight and/or premature infants within one week of discharge from eight neonatal intensive care units. Eight infants (0.7%) had episodes of apnea greater than 30 seconds in duration, all of which were accompanied by bradycardia less than 100 beats per minute; 25 infants (2.3%) had a total of 36 apneic episodes between 20 and 30 seconds in duration, 29 of which were accompanied by bradycardia less than or equal to 100 beats per minute; and 19 infants (1.7%) had episodes of bradycardia less than or equal to 50 beats per minute without prolonged apnea (as shown by a lack of breathing movement). Five infants had ventricular premature beats (including one with ventricular tachycardia). Eleven infants had supraventricular premature beats (including two with supraventricular tachycardia and one with preexcitation). Four infants had both supraventricular and ventricular premature beats. Two infants had preexcitation. Eleven infants who underwent 24-hour recordings died. Five infants were victims of sudden infant death syndrome. One infant death was sudden and unexpected and was attributed to bronchopneumonia. Two deaths were associated with congenital heart disease and three were associated with major cerebral disorders. None of the six babies who died suddenly and unexpectedly had apnea greater than or equal to 20 seconds, bradycardia less than or equal to 50 beats per minute, or cardiac arrhythmias on their 24-hour recordings.

Apnea↗
PubMed1981

Mechanism of molybdate activation of adenylate cyclase.

Molybdate activation of rat liver plasma membrane adenylate cyclase has been examined and compared with the effect of glucagon, Gpp(NH)p and fluoride. Glucagon does not stimulate the detergent solubilized enzyme though molybdate, fluoride, and Gpp(NH)p are effective in this regard. The stimulatory effects of either fluoride or molybdate are additive with those of GTP and do not require guanyl nucleotide to evoke their activation. Neither fluoride nor molybdate can substitute for GTP when glucagon is the activator of rat liver adenyl cyclase. The stimulatory effects of either ion on adenylate cyclase are additive with that produced by glucagon. Activation of adenylate cyclase by either molybdate or fluoride occurs by a mechanism distinct from that of glucagon or guanyl nucleotide. The data presented her suggest that fluoride and molybdate may act via in a similar mechanism of action. Neither ion displays a lag in activation of adenylate cyclase. The pH profiles of fluoride and molybdate-stimulated adenylate cyclase activity are similar, and distinct from guanyl nucleotide-stimulated activity. Cholera toxin treatment of adenylate cyclase blocks fluoride and molybdate stimulation of the enzyme to the same extent, while enhancing the activation obtained with GTP and hormones.

Adenylyl Cyclases↗
PubMed1981

The relationship between plasma membrane lipid composition and physical-chemical properties. II. Effect of phospholipid fatty acid modulation on plasma membrane physical properties and enzymatic activities.

The fatty acid composition of plasma membrane phospholipids of the murine T lymphocyte tumor EL4 were systematically modified in an attempt to understand the relationship between lipid bilayer composition and plasma membrane physical and biological properties. Two plasma membrane enzyme activities, adenylate cyclase and ouabain-sensitive (Na+ + K+)-ATPase, were measured in normal and fatty acid-substituted EL4 plasma membrane fractions. The fatty acid effect on enzyme activities was similar to previously reported effects of fatty acids on cytotoxic T cell function. The activity of both enzymes was inhibited by saturated fatty acids, while unsaturated fatty acids had a moderate enhancing effect on both enzyme activities. Using two different nitroxide derivatives of stearic acid, the order parameter and approximate rotational correlation times were calculated from ESR spectra of normal and fatty acid-modified plasma membranes. No significant differences was found in either parameter in these membranes. These results, in conjunction with earlier data from our laboratory and others, suggest that caution should be exercised in inferring changes in membrane 'fluidity' based on lipid modulation of biological membranes.

Adenylyl Cyclases↗
PubMed1981

ATP-dependent activation of adenylate cyclase.

Incubation of rat liver plasma membranes with MgCl2, ATP, and an ATP-regenerating system at 4 degrees C provides a 4-7-fold persistent activation of adenylate cyclase. Enzyme activation is time-dependent and 48 h of incubation is usually required to achieve maximal stimulation of adenylate cyclase activity. The activation described is not affected by GTP, cAMP, or cGMP, and does not occur when ATP is replaced by a nonphosphorylating analogue, adenyl-5'-imidodiphosphate. In addition to ATP, the activation requires Mg2+ and an ATP-regenerating system. The activation described is not additive with that produced by fluoride and analysis of basal and fluoride activities following extended incubation for 48 h reveals identical activities which decay at the same rate. These results are consistent with our model (11) which invokes phosphorylation-dephosphorylation mechanisms in regulating adenylate cyclase activity.

Adenosine Triphosphate↗
PubMed1980

An explanation for failure of impedance apnoea alarm systems.

24-hour recordings of the ECG and respiration, the latter from an impedance technique, have shown a phenomenon which could account for hitherto unexplained failures of impedance apnoea alarm systems. Whenever apnoea is accompanied by bradycardia there is a pronounced increase in the amplitude of the cardiac impulse on the respiration carrier. This imitates the respiration signal and prevents the alarm from sounding. Conversely, apnoea unaccompanied by bradycardia does not present this problem and is detected by the alarm. If impedance alarm systems are to be used to detect apnoea they must be accompanied by a heart rate (ECG) detector.

Apnea↗
PubMed1980

Human ecology and the geographic distribution of physician assistants.

Ecological characteristics of states were correlated with measures of the geographic distribution of physician assistants, and, for comparative purposes, of new physician licenses. It was hypothesized that prior physician-to-population ratios, the distribution of physician assistant training opportunities, and the nature of state laws regulating physician assistants also would affect the geographic distribution of physician assistants. Population size, of course, is strongly correlated with the total number of both groups in the various states. When numbers relative to population are considered, physician assistants are concentrated in states with extensive training opportunities and, to a lesser extent, favorable laws. In contrast, new physician licenses tend to be concentrated in states that already have high physician-to-population ratios.

Ecology↗
PubMed1980

Aseptic necrosis of the femoral head in corticosteroid-treated pulmonary disease.

During a ten-year period, aseptic necrosis of the femoral head developed in six patients with pulmonary disease treated with corticosteroids. Five of the six patients had severe bronchial asthma. The sixth patient had desquamative interstitial pneumonia. The literature provides some insight into the possible pathogenesis of corticosteroid-related aseptic necrosis of the femoral head and factors that may prevent this complication.

Adult↗
PubMed1979

Activation of adenylate cyclase by molybdate.

The effect of molybdate on adenylate cyclase (EC 4.6.1.1) in rat liver plasma membranes has been examined. The apparent K alpha for molybdate activation of the enzyme is 4.5 mM, and maximal, 7-fold stimulation is achieved at 50 mM. The observed increase in cAMP formation in the adenylate cyclase assay is not due to: (a) an inhibition of ATP hydrolysis; (b) a molybdate-catalyzed conversion of ATP to cAMP; (c) an inhibition of cAMP hydrolysis; or (d) an artifact in the isolation of cAMP formed in the reaction. Molybdate activation of adenylate cyclase is a general phenomenon exhibited by the enzyme in brain, cardiac, and renal tissue homogenates and in erythrocyte ghosts. However, like fluoride and guanyl-5'-yl imidodiphosphate (Gpp(NH)p), molybdate does not activate the soluble rat testicular adenylate cyclase. Molybdate is a reversible activator of adenylate cyclase. Activation is not due to an increase in ionic strength and is independent of the salt used to introduce molybdate. Molybdate does not activate adenylate cyclase previously stimulated with Gpp(NH)p or fluoride. At concentration greater than 20 mM, molybdate inhibits fluoride-stimulated adenylate cyclase, and at concentrations greater than 100 mM, molybdate stimulation of basal adenylate cyclase activity is diminished.

Adenylyl Cyclases↗
PubMed1979

Pseudomonas cepacia resistance to antibacterials.

Reproducible growth rates of Pseudomonas cepacia were obtained. P. cepacia had a markedly different resistance pattern to single and combined antibacterials from that characteristic of Pseudomonas aeruginosa. Benzalkonium and chlorhexidine were more active against log phase P. cepacia than against log phase P. aeruginosa, but polymyxin B sulfate was inactive against log phase P. cepacia at all concentrations tested (smaller than or equal to 16 units/ml). Antagonism of antibacterial activity between edetate disodium-benzalkonium and edetate disodium-chlorhexidine combinations was marked with 16-hr P. cepacia and with 16-hr Staphylococcus aureus. Phenylethanol-benzalkonium and phenylethanolchlorhexidine combinations had no more than additive activity against log phase P. cepacia. These results have relevance to hospital disinfection and preservation of pharmaceutical solutions.

Anti-Bacterial Agents↗