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Biomedical subjects

M M Walker

Publications and source records attributed to M M Walker.

At least 91 records · Page 5Linked to original sources
PubMed1986

Attempts to train goldfish to respond to magnetic field stimuli.

Two different conditioning procedures, one appetitive and the other aversive, were used in separate attempts to demonstrate response to magnetic fields in the goldfish, Carassius auratus. Our results lead us to question those of an orientation experiment by Becker, although we recognize the possibility that goldfish may be sensitive primarily to magnetic field direction rather than intensity and that their directional sensitivity may be evidenced most readily by orientation in the field.

Animals↗
PubMed1983

Evaluation of bonding of bone to inorganic crystal surfaces.

It is known that bone will adhere strongly to dense hydroxyapatite. Evidence is presented to show that bone will adhere to calcite as well, and a theory is proposed to explain the bonding of bone to both these materials. While primarily of interest as a pedagogical tool for evaluating the bonding of bone to other materials, calcite may also be of clinical use as packing material for orthopaedic or dental defects.

Adhesiveness↗
PubMed1982

Further studies on the effects of intravenously administered 6-hydroxydopamine on the median eminence of the rat.

6-Hydroxydopamine (6-OHDA) given i.v. in a dose of 150 mg/kg to adult male Sprague-Dawley rats produces at 24 h a complete depletion of median eminence (ME) and neurointermediate lobe (NIL) catecholamines (CA), as judged by Falck-Hillarp fluorescence histochemistry, leaving the remainder of the hypothalamus substantially unaltered. Restoration of a normal fluorescence histochemical appearance took place over 35 days, apparently due to regeneration of CA-containing terminals. Administration of desipramine prior to 6-OHDA injection modified its effect; depletion was largely confined to the midline region of the external layer of the ME and to the NIL, suggesting that these regions contain dopaminergic terminals. Microspectrofluorometric methods were used in an attempt to verify this conclusion. It is suggested that this technique provides a model for establishing the role of ME and NIL CA-containing structures in control of pituitary gland function.

Animals↗
PubMed1982

Immunoenhancing activity of NPT 15392: a potential immune response modifier.

NPT 15392, a new immunomodulating compound related to inosine in structure and isoprinosine in action, enhances T-cell dependent immune responses. Antibody responses to sheep red blood cells are augmented two to threefold in mice receiving NPT 15392 while T-cell independent antibody responses to TNP-LPS are unaffected. NPT 15392 does not enhance or alter the number of clonable B cells. This drug also increases cytotoxic T-lymphocyte responses to allogeneic tumor cells but does not alter the number of cytotoxic precursor cells. Immature hematopoietic cell classes (clonable progenitor cells) were also monitored and found not to be influenced by NPT 15392.

Adjuvants, Immunologic↗
PubMed1981

Inhibition of cytotoxic T-cell clonal expansion by cyclophosphamide and the recovery of cytotoxic T-lymphocyte precursors by supernatants from mixed-lymphocyte cultures.

Spleen cells from mice treated with cyclophosphamide (150 mg/kg) and cultured at suboptimal concentrations do not generate a cytotoxic T-lymphocyte (CTL) response to allogeneic tumor cells. The reduced response of spleen cells from cyclophosphamide-treated mice is not due to the elimination of CTL precursors because normal responses are obtained by the addition of a helper factor(s) derived from mixed lymphocyte culture supernatants. The results indicate that helper cells, required for development of CTL responses to tumor alloantigens, are eliminated by cyclophosphamide in the absence of evident toxicity to CTL precursors.

Animals↗
PubMed1979

Compulsory admission to hospital: an operational review of the Mental Health (Scotland) Act 1960.

The working of the Mental Health (Scotland) Act 1960 is examined by analysis of compulsory admissions both nationally and to one Glasgow hospital. Comparisons are drwn with England and Wales. Despite a six-fold increase in admissions since 1945 the use of compulsory powers has remained almost constant. It is suggested that an annual number of 45 compulsory admissions per 100,000 population may represent an inevitable basic level as foreseen by the Royal Commission in 1957. Section 31 ('Emergency Recommendation') secures 80 per cent of Part IV admissions, and Section 24 ('Full Recommendation') is employed in only 25 per cent. Part V accounts for only 300 admissions per annum, mostly remands for psychiatric report. Two suggestions are made for possible future amendments to the Act.

Adult↗
PubMed1978

Cardiovascular and behavioral effects of intracisternal 6-hydroxydopamine in the rabbit.

Acute effects of 6-hydroxydopamine (6-OHDA, 400--900 microgram kg-1 intracisternally, i.c.i.) consisted of bradycardia and hypertension, maximal 2--3 h after injection and preceded after some doses by a phase of hypotension. This pattern was obtained in completely conscious rabbits and after propanidid and sodium pentobarbitone anesthesia. After 600 microgram kg-1 i.c.i. 6-OHDA the peak rise in blood pressure (25 +/- 3.8 mm Hg) was due to a rise in peripheral resistance involving particularly renal and intestinal beds. Suprapontine mechanisms contributed to both hypertension and bradycardia. Giving pontine rabbits 6-OHDA elicited a short-latency fall in blood pressure, resembling the hypotensive phase in intact animals. Chronic effects 7 days after 600 microgram kg-1 included a rapid loss of 10% of body weight associated with reduction in food and water intake. To avoid secondary circulatory effects the rabbits were artificially fed, halving the weight loss. At 7 days blood pressure had fallen by 7.4 +/- 2.3 mm Hg probably owing to this residual weight loss. From experiments involving administration of phenotolamine and clonidine in intact rabbits and the responses of pontine animals it is likely that both descending and ascending catecholaminergic pathways have inhibitory effects on blood pressure, though some of the pathways may also be excitatory. Absence of specific chronic circulatory changes may be due to compensation through parallel pathways involving other transmitters.

Anesthesia↗
PubMed1976

Ultrasonic enhancement of nitrogen mustard cytotoxicity in mouse leukemia.

Mouse leukemia L1210 cells were exposed to continuous wave 2 MHz, 10 W/cm(2) ultrasound for 10 minutes while suspended in nitrogen mustard solution in vitro. Mice subsequently inoculated with these cells had longer survival times than control animals that received cells exposed to the drug but not ultrasound. Without the drug, ultrasound did not alter survival time. Tracer studies revealed increased cellular accumulation of drug under the influence of ultrasound.

Animals↗
PubMed1976

Effect of 1-methyl-1-nitrosourea and streptozotocin on glucose-induced insulin secretion by isolated islets of Langerhans.

The present experiments were designed to compare the effects of streptozotocin and 1-methyl-1-nitrosourea upon glucose-induced insulin secretion by isolated islets of Langerhans. Both drugs depressed the insulin response at one and two hours incubation but higher molar concentrations of the nitrosourea were required to produce the same level of inhibition as streptozotocin, a difference perhaps related to the latter's glucose moiety.

Animals↗
PubMed1975

The radiological diagnosis of "avascular" renal tumours.

In the past 9 years we have encountered 3 renal space-occupying lesions, which were "avascular" at arteriography but which appeared to be tumours, as shown by renal puncture of "antegrade" pyelography, All had an irregular inner border demonstrated. The investigation and radiological diagnosis of such masses is discussed thad compared with that of renalcysts.

Abscess↗
PubMedDate not supplied

Human papillomavirus DNA in the urogenital tracts of men with genital dermatoses: evidence for multifocal infection.

In an attempt to assess the multifocal nature of anogenital HPV infection in men, skin biopsies, urethral swabs and urine specimens were obtained from 100 men with genital dermatoses. The specimens were examined for the presence of human papillomavirus (HPV) types 6, 11, 16, 18, 31 and 33 using the polymerase chain reaction and Southern blotting techniques. HPV DNA was detected in one or more specimens from 39 patients, that is 29 of 100 biopsy specimens, 21 (25%) of 85 urethral swab specimens and 6 (10%) of 59 urine specimens. HPV DNA was more common in men with at least 20 lifetime sexual partners and in those who gave a history of anogenital warts. Twelve (18%) of 66 biopsy specimens with no histological evidence of warty change or neoplasia had detectable HPV DNA. HPV DNA was detected no more frequently in the urethral and urine specimens from men with histological evidence of warts or neoplasia than from men without such changes. HPV types 6 and 11 were most common in biopsy specimens with histological changes of typical HPV infection. HPV type 16 was commonest in biopsy specimens with neoplasia and type 18 with other changes. Furthermore, 'high-risk' HPV types were found proportionately more often in urethral swab and urine specimens than in biopsy specimens. There was generally a poor correlation between the detection of HPV DNA at the different sites. A greater understanding of the role of HPV in the production of genital abnormalities is required in order to develop a rational approach to the management of these patients.

Adult↗