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Biomedical subjects

J Morton

Publications and source records attributed to J Morton.

At least 19 recordsLinked to original sources
PubMed1992

Situational factors and thought processes associated with unprotected intercourse in heterosexual students.

Heterosexual students were asked to recall two sexual encounters from the preceding six months: one in which they had unprotected intercourse ('unsafe' encounter) and one in which they resisted a strong temptation to have unprotected intercourse ('safe' encounter). The aims were to record justifications for unprotected intercourse that respondents had given themselves during the unsafe encounter and to identify factors that distinguished between the encounters. In respondents recalling an unsafe encounter (n = 284), the most common self-justification reported was that there was no need for concern since measures to avoid pregnancy had been taken. The first factor that emerged from a Factor Analysis of the self-justification data involved using perceptible characteristics to infer that the partner was unlikely to be infected. Among respondents recalling both encounters (n = 173), there was a trend for type of partner to distinguish between the encounters. With this variable controlled (n = 115), desires, knowledge of condom availability, communication about condom use, degree of boredom, and level of intoxication differentiated between the encounters. The results are discussed in relation to those obtained in our earlier study of gay men.

Adolescent↗
PubMed1992

Can autism be predicted on the basis of infant screening tests?

The authors examined infant hearing and vision screening tests for a group of children subsequently diagnosed as autistic and compared them with a group of children suffering from non-specific developmental delay, as well as with a random sample of records. Four categories (motor, vision, hearing and language, social) were investigated at three ages: six, 12 and 18 months. The random sample group had a low incidence of reported problems at all ages. The learning-disabled group had a sharp increase in reported abnormalities in all categories at 12 months. The autistic group had a selective increase in the social category alone at 18 months.

Autistic Disorder↗
PubMed1992

Cementless total hip arthroplasty in renal transplant patients.

Twenty-seven cementless total hip arthroplasties were performed in 17 steroid-dependent renal transplant patients. The average age at operation was 39 years, and the average daily dose of prednisone was 10.9 mg. At a mean of 48 months post-surgery, all patients had good to excellent hip ratings on clinical examination and the results compared favorably with 235 non-steroid-dependent age-matched patients using the identical prosthetic hip system. The results of this study suggest that long-term immunosuppression does not prevent bone ingrowth. Noncemented total hip arthroplasty appears to be a reasonable therapeutic option for end-stage osteonecrosis in steroid-dependent renal transplant patients.

Adult↗
PubMed1991

Newborns' preferential tracking of face-like stimuli and its subsequent decline.

Goren, Sarty, and Wu (1975) claimed that newborn infants will follow a slowly moving schematic face stimulus with their head and eyes further than they will follow scrambled faces or blank stimuli. Despite the far-reaching theoretical importance of this finding, it has remained controversial and been largely ignored. In Experiment 1 we replicate the basic findings of the study. In Experiment 2 we attempt a second replication in a different maternity hospital, and extend the original findings with evidence suggesting that both the particular configuration of features, and some aspects of the features themselves, are important for preferential tracking in the first hour of life. In Experiment 3 we use a different technique to trace the preferential tracking of faces over the first five months of life. The preferential tracking of faces declines during the second month. The possible causes and consequences of this observation are discussed.

Attention↗
PubMed1991

The cognitive basis of a biological disorder: autism.

This article summarizes recent evidence indicating that individuals suffering from autism have a specific problem in understanding intentions and beliefs. We propose that this problem arises because they are incapable of forming a special kind of mental representation. A single cognitive deficit defines what is common to all autistic individuals. In contrast there is a wide range of proposals for the biological origins of the disorder.

Autistic Disorder↗
PubMed1991

A simple technique for irradiation of recto-anal cancers with electrons using an internal anal shield.

A method of treating the primary site of recto-anal cancers using an en face electron beam in combination with an internal lead shield in the anus has been developed. Dose measurements using lithium fluoride thermoluminescent dosimetry indicate that the internal anal shield reduces the dose to the uninvolved anal wall by up to a factor of two while leaving the dose to the primary tumor site unaffected. Because the internal anal shield is placed in the anus during treatment, this system leads to a more precise daily positioning of the shield compared to the setup using an external shield alone. This technique has been used to treat two patients with anal cancer who tolerated the treatment well with no acute side effects. Both patients are now disease free, more than 30 months after their radiation treatment, without any treatment-related sequelae.

Aged↗
PubMed1991

Effect of short-course indomethacin on heterotopic bone formation after uncemented total hip arthroplasty.

One hundred consecutive total hip arthroplasties (THA) were allocated into two groups: 92 patients received 25 mg of indomethacin three times daily for 10 days starting on the first postoperative day; 108 patients received no prophylactic treatment. Clinical examination and radiographs were evaluated by an independent observer at 3, 6, 12, and 24 postoperative months. No difference was noted at the bone-prosthesis interface between the two groups. Short-course indomethacin was felt to deter heterotopic bone formation significantly, while having no deleterious effect on stabilization of the St. Michael's madreporic system. Clinical examination and radiographs were evaluated by an independent observer at 3 and 6 postoperative months; all patients have continued to be observed, with an average follow-up period of 2 years following surgery.

Bone Cements↗
PubMed1991

CONSPEC and CONLERN: a two-process theory of infant face recognition.

Evidence from newborns leads to the conclusion that infants are born with some information about the structure of faces. This structural information, termed CONSPEC, guides the preference for facelike patterns found in newborn infants. CONSPEC is contrasted with a device termed CONLERN, which is responsible for learning about the visual characteristics of conspecifics. In the human infant, CONLERN does not influence looking behavior until 2 months of age. The distinction between these 2 independent mechanisms allows a reconciliation of the conflicting data on the development of face recognition in human infants. Finally, evidence from another species, the domestic chick, for which a similar 2-process theory has already been put forward, is discussed. The new nomenclature is applied to the chick and used as a basis for comparison with the infant.

Arousal↗
PubMed1991

Aseptic loosening in total hip implants: the role of polyethylene wear debris.

Radiologic and routine histologic examinations, transmission electron microscopy and scanning electron microscopy were carried out on membranes retrieved from the following hip implant prostheses: loose cemented metal-on-polyethylene, resorptive cysts around fixed cemented metal-on-polyethylene, cemented without polyethylene (Thompson), noncemented without polyethylene (Moore), loose ceramic-on-ceramic and loose noncemented metal-on-polyethylene. From histologic analysis the most common factor in the membranes reviewed, in terms of production of multinucleated giant cells, is the presence of polyethylene wear debris. Neither loosening of the implant nor the presence or absence of bone cement produces such cells within the membrane.

Acetabulum↗
PubMed1990

Regulation of calcium concentrations in synaptosomes: alpha 2-adrenoceptors reduce free Ca2+ by closure of N-type Ca2+ channels.

The relationship between intrasynaptosomal total (CaT) and free ([Ca2+]i) calcium and 45Ca accumulation was studied under physiological and K(+)-depolarised conditions in rat cortical synaptosomes. Under physiological conditions, CaT (10.7 mM) was approximately 10,000 times higher than [Ca2+]i (118 nM), showing that there is a large reservoir of sequestered calcium in synaptosomes. 45Ca accumulation was rapid (initial rate, 3.4 nmol/mg protein/min), substantial (7 nmol/mg protein in 2 min), and depolarisation dependent, and reached equilibrium after 5 min. At equilibrium, only 10% of CaT was freely exchangeable. This pool was much larger than the free Ca2+ pool. CaT, [Ca2+]i, and 45Ca accumulations were directly related to the Ca2+ concentration in the buffer, suggesting that [Ca2+]i is not highly conserved but is maintained by simple equilibria between the various pools. Clonidine reduced 45Ca accumulation in a time- and dose-dependent manner. Maximum inhibition (40% at 100 microM) occurred at 2 min and the IC50 was 80 nM. The reduction caused by clonidine (1 microM) reached equilibrium after 5 min, but this equilibrium value was lower than in controls, suggesting that clonidine changes the exchangeable Ca2+ pool size. The effects of clonidine (1 microM) on [Ca2+]i (26% reduction) and on 45Ca accumulation (24% reduction) were most apparent under physiological conditions. However, while it was not dependent on depolarisation, it did not occur in physiological buffer containing low K+ concentration (0.1-1 mM). The inhibitory effect of clonidine on 45Ca accumulation is receptor mediated as it was antagonised by idazoxan (1 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The epidemiology of anorexia nervosa in South Australia.

A survey of 5,705 pupils in girls' schools in South Australia revealed that the one year prevalence of cases of anorexia nervosa, diagnosed according to DSM-III criteria, was 1.05 cases per thousand of the population studied. This study has a number of advantages in comparison to the majority of other school-based surveys, and confirms that descriptions of anorexia nervosa as a disorder of epidemic proportions may be premature.

Adolescent↗
PubMed1989

Isolation of a novel morphinan 3-O-diglucuronide metabolite from dog urine.

Following oral administration of the narcotic antagonist nalmefene [17-(cyclopropylmethyl)-4,5 alpha-epoxy-6-methylenemorphinan-3,14-diol] labeled with 14C to the dog, approximately 50% of the dose was excreted in the urine as a highly polar water-soluble conjugate. Although this major metabolite could be hydrolyzed with beta-glucuronidase to yield nalmefene, the intact conjugate was chromatographically more polar on reversed-phase high-performance liquid chromatography (HPLC) than authentic nalmefene 3-O-glucuronide. Milligram quantities of the metabolite were subsequently isolated and subjected to fast atom bombardment (FAB) mass spectral and nuclear magnetic resonance (NMR) analyses. The conjugate was identified as nalmefene 3-O-beta-diglucuronide with a 1,2-beta linkage between the two glucuronic acids. It is unlikely that this novel form of conjugate is unique to nalmefene and it is probably a metabolite of other morphinans and/or similar drugs in the dog. Nalmefene 3-O-diglucuronide is not a metabolite of nalmefene in man.

Animals↗
PubMed1989

Secretion of antidiuretic hormone in neurosurgical patients: appropriate or inappropriate?

In neurosurgical patients with hyponatraemia (plasma sodium less than 130 mmol/l) and natriuresis, increased antidiuretic hormone (ADH) secretion may be appropriate rather than inappropriate. Ten such patients were studied prospectively to assess circulating ADH concentration and body fluid volumes. Compared with a control group, the mean plasma ADH level was significantly elevated (0.9 pmol/l (s.e.m. = 0.2) versus 0.2 pmol/l (s.e.m. = 0.1], the total body water was normal (101% (s.e.m. = 3) versus 100% (s.e.m. = 6], while the blood volume was significantly reduced (89% (s.e.m. = 3) versus 104% (s.e.m. = 5]. The elevated ADH level was therefore appropriate to a reduced blood volume. This suggests that, in neurosurgical patients with hyponatraemia, fluid restriction could be dangerous. Serial observations in this small group of patients showed that salt replacement and normal fluid intake resulted in a fall in the elevated ADH levels.

Acute Disease↗
PubMed1989

Are fixed-dose oestrogen/progestogen combinations ideal for all HRT users?

Although progestogens protect the endometrium against excessive oestrogen-induced stimulation, they can cause adverse symptomatic and psychological effects and may have undesirable metabolic consequences. Thus, the minimum progestogen dose which results in consistent endometrial transformation should be prescribed. To define this dose for norethisterone and dl-norgestrel, 197 endometrial samples obtained from postmenopausal women receiving conjugated equine oestrogens (0.625 mg or 1.25 mg daily) with one of six doses of norethisterone (or the acetate), or one of three doses of dl-norgestrel added for the first 12 days of each calendar month were examined with the light microscope; 109 samples were also assessed by transmission electron microscopy. There was an inverse relation between the percentage of samples showing proliferative features and the progestogen dose. However, proliferative endometrium was observed in 6% of samples with the highest dose of dl-norgestrel (500 micrograms) and in 3% of samples with 2.5 mg norethisterone. Conversely, complete secretory transformation was observed in 25% of samples with the lowest dose of norethisterone (0.1 mg) and in 40% of samples with 75 micrograms dl-norgestrel. Mild atypical hyperplasia was diagnosed in four samples. There was a wide inter-patient variation in response and none of the nine progestogen dose regimens induced secretory change in every patient.

Cell Division↗
PubMed1989

Bulimia: symptoms and syndromes in an urban population.

The widely used DSM-III criteria for the diagnosis of bulimia essentially define bulimia as a syndrome of guilty, secretive and subjectively hard to control binge over-eating. A self-report questionnaire for bulimic behavior was administered to three community and two hospital populations in South Australia. 13% of females in the community samples could be categorized as bulimic according to the DSM-III criteria. Those criteria did not adequately define the behaviour of patients in treatment for bulimia in a Weight Disorders Unit, 85% of whom not only binged, but induced vomiting afterwards. When diagnostic criteria were more closely aligned to clinical experience, the prevalence of bulimia in the community appeared closer to 1-2%. New DSM criteria (DSM-III-R) have been proposed and prevalence rates using them fell within the 1-2% range.

Adolescent↗