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Biomedical subjects

R A Gardner

Publications and source records attributed to R A Gardner.

At least 19 recordsLinked to original sources
PubMed1992

Categorical replies to categorical questions by cross-fostered chimpanzees.

The chimpanzees Washoe, Moja, Tatu, and Dar were reared under human cross-fostering conditions that included the use of American Sign Language (ASL) as the medium of two-way communication. In the course of everyday conversation they were asked, in signs, the Wh-questions that are typically asked of young children. In earlier studies, extensive samples showed a pattern of replies, most significantly a developmental sequence, that closely matched the pattern found in the replies of young children. Part 1 of this report is based on a special sample taken when Tatu was 63 months old and Dar was 56 months old, in which experimenters used a large pool of nameable objects, and asked a naming question and at least one descriptive question about the same object in the same context. Tatu and Dar replied to naming questions (WHAT THAT? or WHAT NAME THAT?) with signs that were nouns and to descriptive questions with signs that were modifiers: possessive pronouns for WHOSE THAT?, colors for WHAT COLOR THAT?, and materials for WHAT THAT MAKE FROM? Part 2 is a reanalysis of the Part 1 sample and several other samples of replies, demonstrating that even when their reply was incorrect, these chimpanzees usually replied with a sign from the category specified by the question. The continuities that biologists seek are continuities of laws, patterns of resemblance rather than overlapping data points. Results reported here add depth to the patterns demonstrated in earlier studies.

Animal Communication↗
PubMed1988

Schizotrypanum in British bats.

Two species of Schizotrypanum, T. (S.) dionisii and T. (S.) vespertilionis, were identified from British bats. Laboratory studies on stocks of isolated trypanosomes from 5 species of bat (Pipistrellus pipistrellus, Nyctalus leisleri, N. noctula, Eptesicus serotinus and Myotis brandti) indicated that the predominant species was T. d. dionisii. Collections and dissection of the bat bug Cimex pipistrelli from bat roosts revealed flagellate infection in a total of 12 out of 20 bugs; 7 of these bugs had metacyclic trypanosomes present. C. pipistrelli and the human bed bug, C. lectularius were reared in the laboratory and allowed to feed on wild-caught bats known to be infected with T. d. dionisii. Development occurred in both species of Cimex. Cimex spp. could be used to detect subpatent Schizotrypanum infections by xenodiagnosis. This technique was used to test the parasitological status of bats collected in the wild or reared in captivity. On a single occasion an apparent transmission of T. d. dionisii to an uninfected (by xenodiagnosis) laboratory reared bat was achieved. A stock of Schizotrypanum isolated from a wild-caught C. pipistrelli collected in a N. leisteri roost was identified by DNA buoyant density centrifugation as T. (S.) vespertilionis. A P. pipistrellus known to be infected with T. d. dionisii was found to have cyst-like structures in thoracic skeletal muscle containing amastigotes. The study provided the strongest evidence yet that C. pipistrelli is the vector of Schizotrypanum in British bats.

Animals↗
PubMed1988

Trypanosoma (Megatrypanum) incertum from Pipistrellus pipistrellus: development and transmission by cimicid bugs.

Trypanosoma (Megatrypanum) incertum Pittaluga 1905 was found in 33 out of 206 Pipistrellus pipistrellus caught at various sites in Britain. The trypanosome is described from blood smears. Development took place in laboratory-reared Cimex pipistrelli and Cimex lectularius. Epimastigote forms initially multiplied rapidly in the ventriculus and midgut of Cimex. Metacyclic trypanosomes were found in the rectum of both species of Cimex after 8 days when bugs were maintained at 20 degrees C and as early as 3 days at 30 degrees C. Electron microscopy of infected bugs revealed that there was no attachment to epithelial cells of the ventriculus or midgut, but within the rectum epimastigotes were attached by their flagella to the cuticle of the rectum by hemidesmosomes. Transmission was achieved by feeding experimentally infected bugs to bats kept in the laboratory. These bats were negative as judged by xenodiagnosis using laboratory-reared Cimex. Bats which had been caught in the wild demonstrated low-grade or sub-patent parasitaemias (positive in xenodiagnosis) for up to 400 days after the day of capture. Despite an extensive search of impression smears of tissues immediately after trypanosomes first appeared in the blood of experimentally infected bats no multiplicative stages were found.

Animals↗
PubMed1988

Polychromophilus murinus: a malarial parasite of bats: life-history and ultrastructural studies.

Polychromophilus murinus, a malaria parasite of Chiroptera is reported from Myotis daubentoni in England. The vector was suspected to be the ectoparasitic Nycteribiid fly, Nycteribia kolenatii. N. kolenatii collected from wild-caught M. daubentoni were found to have oocysts on the midgut and sporozoites in the salivary glands. Wild-caught N. kolenatii were maintained on two wild-caught M. daubentoni harbouring heavy (patent) infections of P. murinus; both oocysts and sporozoites were found in these flies. The mature oocysts measured 52-71 micron in diameter. Sporozoites were straight or slightly crescentic and had a mean length of 7.4 micron. Electron microscopy of immature and mature oocysts revealed a morphology similar to that of malaria parasites. Sporozoites were also similar in structure to Plasmodium sporozoites and were found in the epithelial cells of the salivary gland and within the lumen; a cytostome was present and transverse sections revealed 21 microtubules arranged evenly around the periphery. Sporozoites were observed within the basement membrane of the salivary gland of N. kolenatii; such sporozoites appeared to be penetrating the gland, a process hitherto not described in malaria parasites. Rickettsia-like bodies were found within the cytoplasm of the epithelial cells of the salivary gland. Exflagellation of microgametocytes was achieved. An ultrastructural study of the gametocytes revealed a structure similar to that described in other Haemoproteidae. A common feature of infected erythrocytes was a projecting erythrocyte membrane. Attempts to find schizogony in impression smears and sections of tissues of two infected M. daubentoni were not successful.

Animals↗
PubMed1987

Babesia vesperuginis: natural and experimental infections in British bats (Microchiroptera).

Babesia vesperuginis is described from blood of two species of British bat: Pipistrellus pipistrellus and Myotis mystacinus. Reticulocytes appeared significantly elevated in blood films of P. pipistrellus infected with B. vesperuginis compared with uninfected laboratory-maintained bats or apparently uninfected wild-caught bats. Infected captive bats had significantly enlarged spleens. B. vesperuginis was transmitted by inoculation of infected blood to 5 uninfected captive P. pipistrellus. The course of infection followed a pattern of a rising parasitaemia accompanied by a rise in reticulocytes, followed by a fall in parasitaemia to low (less than 0.1%) or undetectable levels. When sacrificed, the Babesia-infected bats had significantly lowered blood haemoglobin, significantly raised white blood cell counts and enlarged spleens compared to uninfected bats. Attempts to transmit the parasite to irradiated and athymic 'nude' mice by inoculation of infected blood were unsuccessful. The experimental results and observations of infected wild bats indicate the potential pathogenicity of B. vesperuginis to bats. It is likely that the vector of B. vesperuginis is Argas vespertilionis because no Ixodid ticks were found on P. pistrellus.

Animals↗
PubMed1986

Vocal and gestural responses of cross-fostered chimpanzees.

Ten positive, five neutral, and five negative events were presented to two chimpanzees, Tatu (female, 64 months old) and Dar (male, 56 months old), who had been cross-fostered from birth by human beings. Each event was announced in American Sign Language 10 s before. The announcements and events were common items in the cross-fostering routines and were administered according to a balanced design over a period of 2 months. Vocal and signed responses to the announcements and to the events were recorded. The likelihood of either mode of response depended on affective charge, and the likelihood of vocal and signed responses was positively correlated. Signed responses were more likely than vocal responses; signed responses were more likely to be evoked by announcements than by events, whereas vocal responses were more likely to be evoked by events than by announcements. The type of vocal response depended on the affective charge and on whether the response was immediate (to the event) or anticipatory (to the announcement). Incorporation of signs and phrases from the announcements, and reiteration of signs and phrases within an utterance depended on affective charge, just as they do for human children.

Affect↗
PubMed1985

Signs of intelligence in cross-fostered chimpanzees.

In cross-fostering, the young of one species are reared by adults of another, as in the classical ethological studies of imprinting and song-learning. In our laboratory, infant chimpanzees were reared under human conditions that included two-way communication in American Sign Language (A.S.L.), the gestural language of the deaf in North America. A large body of evidence from five chimpanzees demonstrated stage by stage replication of basic aspects of the acquisition of speech and signs by hearing and deaf children. Here we review evidence that, under double-blind conditions: (i) the chimpanzees communicated information in A.S.L. to human observers; (ii) independent human observers agreed in their identification of the chimpanzee signs, (iii) the chimpanzees could use the signs to refer to natural language categories: DOG for any dog, FLOWER for any flower, SHOE for any shoe.

Animals↗
PubMed1985

Age-related changes in deformability of human erythrocytes.

The present study was designed to further the characterization of age-related changes in the deformability of human erythrocytes. The top (approximately young) and bottom (approximately old) 10% fractions of density-separated red cells from ten normal donors were subjected to graded levels of shear stress in a rheoscope. Measurements were made of steady-state elongation (cells tank treading in a state of dynamic equilibrium) and the time course of shape recovery following abrupt cessation of shear. In parallel with the rheologic experiments, several physical and chemical properties were assayed to determine correlates of mechanical properties. These included mean cell volume, mean corpuscular hemoglobin concentration, type A1 hemoglobin, glucosylation of membrane proteins, and membrane phospholipid and protein concentration. The microrheologic observations revealed that only about 90% of the old cells retained their capacity to tank tread. However, the tank-treading cells elongated less than their younger counterparts at corresponding levels of shear stress, thus demonstrating a reduced level of deformability. Further analysis of the data indicates that increases in membrane viscosity and elastic modulus along with a significant loss in excess surface area contribute to the limitation of the ability of the older cells to change shape.

Adult↗
PubMed1985

Microrheologic investigation of erythrocyte deformability in diabetes mellitus.

This study was undertaken to determine whether diabetes alters the viscoelastic properties of erythrocytes. The oldest and youngest 10% fractions of circulating red cells were separated by centrifugation of freshly drawn blood obtained from ten diabetics with disease of one to 20 years' duration and from an equal number of age- and sex-matched control subjects. Cells from each fraction were suspended in phosphate-buffered saline, and their rheologic behavior was examined in a rheoscope. The elongation of cells, the percentage of cells that tank-treaded in response to shear stress, tank-treading frequency, and the rate of recovery of cell shape upon cessation of shear stress were determined in the oldest and youngest 10% of cells for diabetics as well as for controls. All four parameters were virtually identical for diabetics and controls. Additional aliquots of cells were taken for assessment of nonenzymatic glucosylation of hemoglobin and cell membrane protein. The absence of any measurable difference in rheologic behavior of cells from diabetic and control subjects, despite substantial differences in nonenzymatic glucosylation of hemoglobin and cell membrane proteins, suggests that the magnitude of glucosylation observed in these cellular constituents does not alter the viscoelastic properties of the cells. The implication of these observations is that microvascular complications of diabetes are not attributable to altered deformability of red cells.

Adult↗
PubMed1984

A vocabulary test for chimpanzees (Pan troglodytes).

Chimpanzees can communicate in American Sign Language (ASL) to independent human observers whose only source of information is the ASL signs of the chimpanzees. A vocabulary test was presented to 4 cross-fostered chimpanzees (4-6 years old). Thirty-five-millimeter color slides were projected on a screen that could be seen by the chimpanzee subject but not by the human observers. There were two observers: O1 was the questioner in the testing room with the subject; O2 was in a different room. Neither observer could see the other, or the responses of the other observer. O1 and O2 agreed in their readings of both correct and incorrect signs, and most of the signs were the correct ASL names of the slides. In order to show that the chimpanzees were naming natural language categories--that the sign DOG could refer to any dog, FLOWER to any flower, SHOE to any shoe--each test trial was a first trial in that test slides were presented only once. Analysis of errors showed that two aspects of the signs, gestural form and conceptual category, governed the distribution of errors.

Animals↗
PubMed1983

A study of variance in measurements of tank-treading frequency in populations of normal human red cells.

The statistical variance in rheoscopic measurements of tank-treading frequency ( TTF ) of normal human red cells has been investigated and the sources of this variance analyzed. Experiments were designed to expose the influence of donor, the stability of a donor's cells over a 2-month period, storage time from venipuncture to testing, cell age, applied shear rate and variations in the rheoscope gap due to trial-to-trial manipulation. The results show that the TTF varies linearly with applied shear rate within the range 20 to 180 s-1 and is strongly dependent on cell age. The slope of the TTF characteristic is not significantly different in cells taken from different, but hematologically normal adults nor does it change significantly over time in a particular donor. TTF measurements may be useful in distinguishing rheologically abnormal cell populations which differ from normal cells by at least 10%.

Adult↗
PubMed1978

Social, legal, and therapeutic changes that should lessen the traumatic effects of divorce on children.

Easing the plight of the divorcing and the divorced requires the efforts of a broad range of professional disciplines. It is not my purpose here to cover in detail the various ways in which different professionals can contribute to this goal. Rather, I will focus on certain specific changes which, if implemented, could prevent and/or lessen some of the psychological traumas attendant to divorce. Some of these changes are already being instituted but are mentioned here because they warrant more widespread appreciation and utilization. Others, to the best of my knowledge, have not yet been made and may never be. My hope is that this presentation will play some small role in bringing about these changes.

Child↗