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Biomedical subjects

L Richardson

Publications and source records attributed to L Richardson.

At least 91 records · Page 5Linked to original sources
PubMed1983

Interference between non-A, non-B and hepatitis B virus infection in chimpanzees.

Pre-existing chronic or concurrent acute non-A, non-B (NANB) virus infection has been found to interfere with hepatitis B virus (HBV) replication and to delay and moderate markedly the appearance of disease related to HBV infection in chimpanzees. The mechanism for this phenomenon remains unclear. These findings are of practical significance for vaccine safety testing and evaluation of methods for virus inactivation in chimpanzees. The possible occurrence of dual NANB and HBV infection requires that prolonged follow-up be carried out. Attempts to carry out inactivation studies on materials containing both types of virus may also provide misleading observations.

Alanine Transaminase↗
PubMed1983

Blood-borne non-A, non-B hepatitis: lack of infectivity of feces from chimpanzees infected with a strain producing cytoplasmic tubular alterations.

Fecal and serum samples from a chimpanzee with acute-phase, blood-borne non-A, non-B hepatitis were administered to four chimpanzees. Fecal material given either intravenously or orally did not result in abnormal levels of alanine aminotransferase or the occurrence of ultrastructural alterations in hepatocellular cytoplasm characteristic of non-A, non-B hepatitis during a one-year period of follow-up. Definite non-A, non-B hepatitis was later demonstrated in two of these animals four weeks after inoculation of acute-phase serum. Thus, feces do not appear to transmit this human strain of blood-borne non-A, non-B hepatitis.

Animals↗
PubMed1983

Specificity and significance of hepatocellular ultrastructural changes in non-A, non-B hepatitis in chimpanzees.

324 liver biopsies from 71 chimpanzees with and without non-A, non-B (NANB) hepatitis have been examined by electron microscopy (E.M.) for hepatocellular changes reported to be associated with this disease. At least 2 types of ultrastructural cytoplasmic alterations were found in each of 23 cases of acute and 6 cases of chronic NANB hepatitis. Nuclear modifications were never seen. Similar ultrastructural alterations were found in infections derived from 9 different human blood borne NANB cases. In 9 animals which had received 5 different inocula, Pfeifer Type I, II, III and IV changes were seen; 3 of the 4 types occurred in 10 animals and 2 of the types in 5 animals. Type II and III changes were almost always seen together. All 4 types of alteration were usually found in biopsies taken near the peak of ALT elevation. Five of 6 animals in whom E.M. changes were detected in serial samples over a 1 1/2 to 4 1/2 year period had concurrent chronic ALT abnormality. Two of these 6 animals did not develop ALT abnormality until years after the original acute episode though E.M. changes were detected throughout this period. There was generally a good correlation between onset and duration of ALT abnormality and period when E.M. changes were detected. All samples from animals not exposed to NANB virus(es) were negative by E.M. Our findings indicate the ultrastructural cytoplasmic alterations to be highly specific for NANB infection. Since each of the 9 isolates produced essentially the same pattern of E.M. changes, it is likely that a single NANB hepatitis virus group accounts for most blood borne NANB hepatitis.

Alanine Transaminase↗
PubMed1982

Preliminary report of an exposure-based, case-control monitoring system for discovering occupational carcinogens.

There is no evidence concerning human carcinogenic potential of most substances to which workers are exposed. A case-control type method has been developed to discover heretofore unsuspected occupational carcinogens. Incident cases of cancer of several sites are ascertained and the subjects are interviewed to obtain detailed job histories. The job histories are subsequently examined by chemists and engineers who infer for each job a list of potential chemical and physical exposures. These lists of exposures then become the basis of case-control type statistical analyses, wherein each site included and each exposure noted in any history are evaluated for possible association. Controls can be selected in the general population, among non-cancer hospital patients or, as we do, among other cancer patients. Preliminary findings from a pilot study in Montreal show that 1) an efficient case ascertainment system and an acceptable interview procedure can be set up, 2) job histories provided by respondents are quite valid, 3) chemists' translations of job histories into histories of chemical exposures seem to be meaningful and useful, and 4) at least one carcinogenic agent, cigarette smoking, is detectable whether a population control series or a cancer control series is used.

Adult↗
PubMed1982

A silver impregnation technique for the study of steroid receptors in central nervous system tissue prepared for autoradiography.

The commonly used silver stains were found to be unsatisfactory for nervous tissue processed for autoradiography. A silver impregnation procedure for central nervous system tissues prepared for the autoradiographic study of steroid receptors is described. The procedure is a combination of several silver and reticular strains made up in solutions containing dimethylsulfoxide. The technique clearly distinguishes perikarya of neurons, brain nuclei and fiber tracts without substantial loss of silver grains, and thus greatly facilitates the identification of steroid receptor nuclei at all levels of the central nervous system.

Animals↗
PubMed1981

Epidemiology of hepatitis B infection in Liberian infants.

To provide background for a hepatitis B vaccine efficacy trial, sera were collected from 0- to 4-year-old Liberian infants and their mothers, on two occasions an average of 14.75 months apart, and tested for serological markers of hepatitis B virus infection. The prevalence of the hepatitis B surface antigen (HBsAg) was 2.9% in the 0- to 6-month age group and 23% in infants 3 to 4 years of age. HBsAg persisted for the 14.75-month average follow-up period in 80.8% of the infants tested. The annual incidence of development of HBsAg was 18.9% for infants less than 1 year of age and 13.6% in infants 3 to 4 years of age. Infants born to HBsAg carrier mothers had significantly higher age-specific prevalence and incidence of hepatitis B virus infection. However, it was estimated that only a minor proportion of hepatitis B infections in Liberia are derived by vertical transmission from carrier mothers.

Adolescent↗
PubMed1980

Equality in medical care under national health insurance in Montreal.

In November 1974, four years after national health insurance in Canada had eliminated all out-of-pocket payment for physicians' services, we surveyed 1559 households in a socially heterogeneous area of Montreal to assess social-class differences in the use of physicians' services. When reported health status as well as age and sex were taken into account, the rates of physician visits during the two-week period preceding the survey were essentially the same in the low, middle, and high economic classes, thus confirming that disparity of access had been reduced. However, relative to other groups, the poor still made considerable use of hospital clinics and emergency rooms for primary care and more of their visits entailed prescriptions and physician-initiated requests to return. The latter observations may indicate that the poor, as compared with other groups consulted the doctor for more advanced conditions. Official statistics showed no increase in the workload of the average physician, although the number of physician visits per person per year had risen steadily. There was no evidence of abuse of "free" medical care by the poor.

Data Collection↗
PubMed1979

Staining calcified tissues in plastic embedding medium.

Two procedures for staining sections of calcified teeth and/or bone embedded in plastic without dissolving the embedding medium were developed to study early bone regeneration in proximity to carbon implants in monkey alveolar bone and tissue degeneration in pathological human bone. These procedures allow differential staining of delicate bone tissues and prevent breakage of sections because the supporting plastic does not have to be removed.

Animals↗
PubMed1978

A modified processing and sectioning technique for hard tissues.

A new procedure for embedding and sectioning hard tissues was developed to study bone regeneration in relation to carbon implants used in crown and bridge preparations of maxillas and mandibles of nonhuman primates. Tissues were fixed in 10 percent neutral buffered formalin, dehydrated in 95 percent and 100 percent ethyl alcohol, and embedded in a modified Spurr's low-viscosity embedding medium. Tissues were sectioned as thin as 50 to 100 micron with a Buehler Isomet Model 11-1180 low speed saw. Unstained sections, as well as tissue stained with hematoxylin and eosin and Gomori's trichrome, were examined with a light microscope. The sections were of high quality without distortion. This new procedure expedited experimental work because decalcification of tissues was not needed and implants did not fragment.

Animals↗
PubMed1977

Automated high-resolution gas chromatographic analysis of psychotropic drugs in biological fluids using open-tubular glass capillary columns. I. Determination of nomifensine in human plasma.

An automated high-resolution gas chromatographic method has been developed for the determination of low levels of the antidepressant psychotropic drug Nomifensine in human plasma. The drug is extracted from alkalinized plasma with diethyl ether and then back-extracted into an acidic aqueous phase. After subsequent extraction into diethyl ether the drug is analysed by gas-liquid chromatography as its heptafluorobutyrate derivative using an OV-101 open-tubular glass capillary column with a nitrogen-specific detector. The propyl and butyl analogues of Nomifensine are used as internal standards, added to the plasma before extraction. The method is accurate, specific and precise, and capable of measuring plasma concentrations down to a level of 2 ng/ml. A preliminary study of the pharmacokinetics of the drug, together with steady-state level measurements in normal individuals receiving therapeutic dosages of Nomifensine, has been made.

Adult↗
PubMed1977

Knife sharpening revolutionized.

A new application has been found for an adhesive-backed, nylon polishing cloth previously used chiefly in the metallurgic field. When adhered to the glass plate of an automatic microtome knife sharpener, the cloth provides a superior sharpening surface and eliminates the need for resurfacing the plate. We have found this new technique simple, inexpensive, and timesaving.

Histology↗
PubMed1976

Mutual visual regard during mother-infant play.

Mutual visual regard was observed in 48 mother-infant dyads during a 6-min. play session. Infant-mother dyads containing 4 mo. -olds displayed significantly more mutual visual regard than dyads containing 6- or 8-mo.-olds. In addition, the more time infants spent in face-to-face interaction with mother, the more smiling they engaged in. No sex difference were observed.

Age Factors↗