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Biomedical subjects

P Collins

Publications and source records attributed to P Collins.

At least 289 records · Page 16Linked to original sources
PubMed1989

The sulcus medianus organ in the fourth cerebral ventricle of the rabbit: a previously undescribed circumventricular organ.

The sulcus medianus of the fourth ventricle in the rabbit contains a previously undescribed circumventricular organ. The cells in this region are predominantly nonciliated. The apical surface of each cell has characteristic microvillous projections with pinocytotic vesicles. The cell body is elongated, with the nucleus situated in the body or basal process; the cytoplasm of the cell is pale and contains microtubules and filaments. The general morphology of the cells is similar to tanycytes found in other circumventricular organs. Supraependymal cells were present on the non-ciliated ependyma in all of the animals examined, sometimes in large numbers.

Animals↗
PubMed1988

Passive protection of calves against experimental infection with Salmonella typhimurium.

Cows were vaccinated with formalin-killed Salmonella typhimurium approximately seven weeks and two weeks before parturition to investigate whether passive immunity could protect their calves against experimental S typhimurium infection. After birth the calves were left with their dam for 48 hours and then separated and fed cold, stored colostrum from their own dam for a further eight days. Oral challenge five days after birth with 10(8) S typhimurium did not result in the death of these calves even when they had absorbed little colostrum. Mortality was reduced to 22 per cent in calves which sucked from vaccinated dams and were then fed colostrum from unvaccinated cows and to 50 per cent in calves born to unvaccinated cows and later fed colostrum from vaccinated animals. Calves which sucked from a vaccinated dam and then received stored colostrum from the same cow excreted salmonellas for significantly shorter periods after challenge and were less often infected at necropsy 28 days after inoculation. Protection was not correlated with the levels of O or H agglutinating antibodies in serum, which were at a maximum 24 hours after sucking and then slowly declined. There was no evidence of an active antibody response in the serum. Measurement of the O and H response of cows after vaccination indicated that the vaccination schedule could be improved. The highest levels of agglutinating antibody were measured between two and three weeks after the first vaccination and there was only a minimal response to the second vaccination before parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Viral sensitivity following the introduction of acyclovir.

Extensive use of acyclovir for the treatment or prevention of herpes simplex and varicella zoster infections in immunocompetent patients has not resulted in significant changes in virus sensitivity. Some minor reductions have been observed, but these have not affected clinical responses. In severely immunosuppressed patients, virus with reduced acyclovir sensitivity has very occasionally been isolated and this has sometimes been associated with clinical resistance. Resistance has, in all but one instance, resulted from the inability of the virus to express thymidine kinase. Follow-up where possible to subsequent recurrences has in all cases revealed sensitive virus. Therefore, resistance to acyclovir in the clinical setting seems to be transient and its significance slight.

Acyclovir↗
PubMed1988

Helicopter transport of patients during acute myocardial infarction.

Initial experience with a regional system of emergency helicopter transport of patients with acute myocardial infarction (AMI) referred for emergent cardiac catheterization and percutaneous transluminal coronary angioplasty (PTCA) is described. Two hundred fifty patients with AMI were transported from within a 150-mile radius to Duke University Medical Center over a 15-month period. All patients were within 12 hours of onset of symptoms. Thrombolytic therapy was administered to 240 (96%) patients (72% before or in-flight). The time to administration of thrombolytic therapy ranged from 30 to 120 minutes (median 180), while the time to arrival in the interventional catheterization laboratory ranged from 105 to 815 minutes (median 300). The flight time was 12 to 77 minutes (median 31). Most patients had 1- or 2-vessel coronary artery disease; the baseline ejection fraction ranged from 27 to 70% (median 42). Transient hypotension was the most common complication both pre-flight and in-flight. Third-degree atrioventricular block and nonsustained ventricular tachycardia were the next most common complications. Ventricular fibrillation or sustained ventricular tachycardia occurred before takeoff in 38 patients (15%). No patients had ventricular fibrillation, asystole or respiratory arrest during transport. Fluid boluses for hypotension were the most common intervention. Five patients required cardiopulmonary resuscitation in-flight; 3 before lift-off and 2 required a brief period of cardiopulmonary resuscitation during sustained ventricular tachycardia. Fourteen patients had pressor therapy, military antishock trousers or both to maintain adequate blood pressure. Neither cardioversion, defibrillation nor intubation were performed in-flight. Thus, inflight complications are infrequent and can be managed en route to an intervention center.(ABSTRACT TRUNCATED AT 250 WORDS)

Aircraft↗
PubMed1988

Selective acceptance of MHC class I-deficient tumor grafts in the brain.

H-2-deficient (H-2-) tumor variants were accepted equally well compared with H-2+ wild-type cells in the brain of syngeneic mice, while the H-2- cells were selectively eliminated when inoculated extracranially. This indicates a specific absence or suppression of the defense against MHC class I-deficient cells in the brain, suggested to be mediated by NK cells. In contrast, T cell-mediated immune reactions could clearly be detected in the brain under the same experimental conditions. This was shown in control experiments where H-2+ tumor cells were rejected from the brain of preimmunized or allogeneic mice. The present findings may be important for the understanding of neurotropic virus infections, immunology and immunotherapy of brain tumors, as well as for the growing interest in tissue grafting within the central nervous system.

Animals↗
PubMed1988

Effects of catecholamines on serum lipoproteins of normally fed and cholesterol-fed rabbits.

The effects of catecholamines on the regulation of lipoprotein metabolism have not been defined. We examined the effects of subcutaneously administered slow-release preparations of norepinephrine (2 mg/kg) and isoproterenol (0.2 mg/kg) on the serum lipoproteins of New Zealand White rabbits. Drugs or control suspension were administered daily to three groups of normally fed and three groups of cholesterol-fed rabbits, and lipoprotein analysis was performed at intervals over a 60-hour period. In the normally fed animals, norepinephrine increased the serum levels of triglyceride and phospholipid by factors of 2.4 (P less than .01) and 1.35 (P less than .05), respectively, compared with control animals at 60 hours, but had no effect on serum cholesterol. All components of serum very low density lipoproteins (VLDL: triglyceride, cholesterol, phospholipid, and protein) were significantly (P less than .01) elevated by norepinephrine in the normally fed animals. In the cholesterol-fed animals, norepinephrine at 60 hours significantly increased total serum cholesterol, triglyceride, and phospholipid concentrations by factors of 1.7 (P less than .05), 5.0 (P less than .01), and 1.6 (P less than .05), respectively, compared with controls. The norepinephrine effects in these animals was due to significant elevation of total VLDL and low density lipoproteins (LDL) and all their elemental components. Isoproterenol produced no significant effect on serum lipoprotein levels in the normally fed rabbit, but in cholesterol-fed animals it produced a rise in total serum VLDL and LDL triglyceride concentrations compared with controls at 60 hours. These data demonstrate that catecholamines are involved in the regulation of lipoprotein metabolism.

Animals↗
PubMed1988

Chronic lymphocytic leukemic (CLL) cells secrete multispecific autoantibodies.

A subset of B cells expressing the CD5 marker, a 67 KD molecule, has been implicated in the pathogenesis of autoimmune disease. To study the immunoglobulin repertoire of CD5+ B cells we investigated chronic lymphocytic leukemic (CLL) cells, since the majority of the malignant clones express CD5. CLL were induced to secrete their IgM in vitro by phorbol 12-myristate 13-acetate (PMA) and the supernatants screened for binding to a panel of autoantigens. Twelve out of 14 CLL clones were autoreactive, binding to Fc of IgG, ssDNA, dsDNA, histones, cardiolipin, or cytoskeletal components. Many also bound to more than one antigen tested for, showing multispecificity. Our data suggest that a high proportion of CD5+ B cells are programmed to secrete multispecific autoantibodies.

Antibodies, Neoplasm↗
PubMed1988

Effect of acyclic pyrimidines related to 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine on herpesviruses.

A series of pyrimidines related to the potent antiherpetic agent 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (1, BW B759U), all containing the same acyclic chain, have been synthesized. Some of the compounds were derivatives of the naturally occurring bases, cytosine, uracil, and thymine; others included compounds in which the 5-position of the cytosine and uracil moieties were substituted by bromo, iodo, fluoro, methyl, and amino groups. Other variations of the cytosine derivatives were the 5-aza, 2-mercapto, 4-methylamino, 4-dimethylamino, and isocytosine congeners. A 4-aminopyrimidine adduct was also made. Antiviral testing showed that 1-[(1,3-dihydroxy-2-propoxy)methyl]cytosine (18, BW A1117U) was equivalent to the guanine analogue in potency against human cytomegalovirus and Epstein Barr virus. Other compounds in the series were largely inactive in antiviral screening against the herpesviruses.

Acyclovir↗
PubMed1988

Calcium retention and increased vascular reactivity caused by a hypothalamic sodium transport inhibitor.

1. Using a previously established method of isolating an active-sodium-transport inhibitor (ASTI) from hypothalamic cell culture medium, the inhibitor was isolated and partially purified from sequential passages through Sephadex G-25 and h.p.l.c., and its effects on de-endothelialized rabbit aortic strips were investigated. 2. ASTI caused a cumulative concentration-dependent increase in tension which reversed slowly after wash, and the wash showed an identical effect on fresh strips. 3. Ouabain, used as a control, also caused a concentration-dependent increase in tension which reached a plateau at a concentration of 10 mmol/l. Both ouabain and ASTI caused a significant potentiation of the vasoconstrictor effect of noradrenaline at concentrations of 1 nmol/l-0.1 mmol/l. 4. Both ASTI and ouabain caused a significantly greater (P less than 0.01) calcium retention than control medium in aortic strips. 5. Incubation of ASTI with prolidase, chymotrypsin and carboxypeptidase A destroyed the vasoconstrictor effects as well as its inhibitory effects on sodium, potassium-dependent adenosine triphosphatase and sodium efflux from erythrocytes, but leucine aminopeptidase was ineffective. 6. These studies suggest that hypothalamic cells in culture release a peptidic inhibitor of active sodium transport which increases vascular reactivity, potentiates vasoconstrictor effects of noradrenaline and causes calcium retention.

Animals↗
PubMed1988

Endothelium-derived relaxing factor and nitroprusside compared in noradrenaline- and K+-contracted rabbit and rat aortae.

1. The effects of endothelium-derived relaxing factor (EDRF) (as stimulated by acetylcholine in the presence of endothelium), sodium nitroprusside and 8-bromocyclic GMP on mechanical relaxation, calcium (45Ca) influx and cyclic GMP levels were studied in isolated rabbit aortic preparations pre-contracted either by noradrenaline or by high (120 mM) extracellular potassium. 2. The results confirmed a relatively greater effect of these three interventions on mechanical relaxation and on reducing calcium influx in noradrenaline-contracted than in potassium-contracted preparations. 3. The increase in cyclic GMP levels induced by sodium nitroprusside, contrary to previous reports, was no greater in noradrenaline-stimulated preparations than in potassium-stimulated preparations, a finding confirmed in rat aortic preparations, and relaxation was not associated with a significant reduction of calcium influx in the potassium-stimulated preparations. 4. Cyclic GMP-mediated relaxation of potassium contraction thus appears to be due to actions of cyclic GMP other than on calcium influx. 5. These findings suggest that cyclic GMP reduces calcium influx more through receptor-operated channels than through voltage-operated channels. 6. The endothelium-dependent acetylcholine-induced elevation of cyclic GMP was reduced both by noradrenaline and by high extracellular potassium, possibly by altering release or activity of EDRF. 7. The sensitivity of the soluble guanylate cyclase system to stimulation by EDRF and nitrovasodilators appears to be greater in rat than rabbit aortic preparations.

Animals↗
PubMed1988

Role of immunoglobulin and peritoneal phagocytes in the protection of rats against salmonella infection.

Intradermal vaccination of rats with heat-killed Salmonella dublin protected against an intraperitoneal challenge of live S dublin. Serum from vaccinated animals administered intraperitoneally protected normal rats against intraperitoneal challenge with S dublin and four other serotypes. Protection was attributed to opsonic antibodies which promoted phagocytosis by mononuclear phagocytes. The opsonin was identified as IgG2a which prevented lysis of macrophages and enabled them to contain the pathogen at the site of infection. In vitro, mononuclear phagocytes killed S dublin for up to two hours after phagocytosis in the presence of immune rat serum.

Animals↗
PubMed1987

Studies on the ontogenesis of the different isoenzymes of Na+, K+-ATPase in rat brain in vivo and in vitro in relation to their regulation and cellular localisation.

Na+,K+ ATPase isoenzyme activities (alpha(+)-high ouabain affinity; alpha low ouabain affinity) were investigated in developing rat brain in vivo and in whole rat brain reaggregating cultures in vitro. The perinatal profile of the two isoenzyme forms in vivo revealed that, although alpha activity predominates in immature (P14.5-P16) brain, the activity alpha(+) form increases more increases more rapidly such that it is predominant at birth in both cerebellum and forebrain. No regional variation in the proportional activities of the two isoenzyme forms was seen perinatally to explain the previously reported, differential sensitivity of the cerebellar alpha isoenzyme to neonatally induced hypothyroidism. Whole rat brain reaggregating cultures seeded at P16 show a normal development of Na+,K+ ATPase isoenzyme activity if grown for 14 days in a serum supplemented medium (S+). Cultivation of whole rat brain reaggregates in serum deprived medium (S-) leads to a retarded development of alpha isoenzyme activity possibly due to the absence of T3 from the medium. Hormonally-induced changes in the development of the brain Na+, K+-ATPase isoenzymes are discussed in relation to their possible function and cellular localization.

Animals↗