Biomedical subjects

R Barnard

Publications and source records attributed to R Barnard.

64 records · Page 4Linked to original sources

PubMed1985

Evidence from the use of monoclonal antibody probes for structural heterogeneity of the growth hormone receptor.

We describe the use of four monoclonal antibodies (MAbs) to the rabbit liver growth hormone (GH) receptor and one raised against purified rat liver GH receptor to characterize liver receptor subtypes which differ in their hormone-binding regions. The anti-(rat liver GH receptor) MAb both inhibited and precipitated rat and rabbit GH receptors, but only one-half of 125I-oGH (ovine GH) binding to liver microsomes could be inhibited by excess antibody. Conversely, only one-half of 125I-anti-(rat GH receptor) MAb binding was inhibited by excess oGH and Scatchard plots for this MAb exhibited two components. Although only 50% of 125I-oGH binding to membranes was inhibited by this MAb, all solubilized receptor could be immunoprecipitated. We postulate two epitopes for the anti-(rat GH receptor) MAb, one located at the hormone-binding site (inhibitory site) and one elsewhere (immunoprecipitating site). A second, rabbit-specific antibody (MAb 7) inhibited 85% of hormone binding but only 30% of 125I-anti-(rat GH receptor) MAb binding to rabbit liver microsomes. A combination of this MAb with the anti-(rat GH receptor) MAb totally inhibited 125I-oGH binding. MAb 7 alone totally inhibited 125I-rat GH binding to rabbit liver microsomes, as it did with 125I-oGH binding to purified receptor. On the basis of these results and others we postulate three types of GH receptor in rabbit liver membranes and ascribe approximate extents of 125I-oGH binding to each. A cytosolic 'GH receptor' which is not poly(ethylene glycol)-precipitable is shown to share five epitopes with 'type 2' microsomal receptors. Purified plasma membrane and endoplasmic reticulum fractions derived from a rabbit liver microsomal preparation have identical antigenic characteristics with respect to the GH-binding region, indicating that the heterogeneity we describe is not related to receptor processing. Of the three types of GH receptor in the plasma membrane of the rabbit (and possibly rat) we postulate that one (type 1) corresponds to the GH receptor involved in stimulating growth and possesses all of the epitopes studied here. A second (type 2) appears to be identical with the cytosolic 'GH receptor' and lacks the epitope for the anti-(rat GH receptor) MAb in the hormone binding site region. A third (type 3) does not possess the epitope for the inhibitory anti-(rabbit GH receptor) MAb, appears not to bind rat GH and is lost during purification. The availability of type-specific MAbs will facilitate assignment of specific functions to liver receptor subtypes which mediate the multiple functions of GH.

Animals↗

PubMed1984

Monoclonal antibodies to the rabbit liver growth hormone receptor: production and characterization.

Monoclonal antibodies to the GH receptor (GHR) have been produced by the application of hybridoma technology to splenic lymphocytes from BALB/C mice immunized with a human (hGH) affinity purified preparation of rabbit liver GHR. Primary screening of 384 wells yielded 4 antibodies able to immunoprecipitate [125I]iodo-hGH complexes with purified GHR and one able to inhibit binding of [125I]iodoovine GH ([125I]iodo-oGH) to rabbit liver microsomes. These cells were cloned and grown as ascitic tumors with loss of 1 of the 4 precipitators. Ascitic fluids contained monoclonal antibodies of high titer (inhibitor and 2 precipitators, 1:2.0 X 10(5); one precipitator, 1:2.0 X 10(4)) and high affinity (precipitators, 2.5-6.0 X 10(9) M-1; inhibitor, high affinity component, 6.4 X 10(10) M-1), which were isotyped as IgG1K and IgG2aK (1 precipitator). These antibodies did not cross-react with rabbit insulin or PRL receptors in the appropriate receptor assays and did not possess antihormone activity. Binding of [125I]iodo-MAb7, the inhibitory antibody, was totally blocked by the addition of excess unlabeled oGH or hGH, although these hormones had no effect on binding of the 125I-labeled precipitators. Scatchard analysis of [125I]iodo-oGH binding in the presence of MAb7 showed decreased binding by loss of sites rather than affinity. Antibody dilution curves and Scatchard plots for MAb7 binding provided evidence for two types of GHR in the rabbit liver, in accord with previously published data based on hormone binding studies. All precipitating antibodies gave an enhancement of [125I] iodo-oGH binding with purified receptor (up to 360% of polyethylene glycol-precipitated control), but only minimal enhancement with solubilized microsomal membranes. This enhancement was shown to be due to an increase in receptor number rather than affinity. After examining a number of hypotheses, we concluded that the enhancement was an artifact resulting from a nonpolyethylene glycol-precipitable species of GHR which could be totally precipitated by the monoclonal antibodies. We have produced and characterized four monoclonal antibodies to the GHR which will be of value in characterizing the structure and function of this receptor.

Animals↗

PubMed1982

Use of serum copper/zinc ratio in patients with large bowel cancer.

The serum copper/zinc ratio was measured in 44 patients bearing primary large bowel malignancies. Measurements were repeated following removal of the primary tumour and again at the time of development of clinical evidence of cancer recurrence in order to evaluate the clinical value of the ratio to accurately reflect the presence or absence of malignancy. Estimation of serum copper levels do reflect the presence of malignancy, but the copper/zinc ratio is of no added value. As other acute phase proteins have been shown to be superior to serum copper as markers for monitoring of cancer patients, it is concluded that in patients with large bowel cancer, monitoring with serum copper/zinc is of no clinical value.

Ceruloplasmin↗

PubMed1982

Tennessee antigen: the predictive value of preoperative and postoperative assays in large-bowel cancer.

Twenty-nine of 31 patients bearing resectable colorectal cancers had elevated levels of serum Tennessee antigen in comparison with only eight of 31 patients for carcinoembryonic antigen. This high detection rate is, however, of limited value since the level of serum Tennessee antigen is not specific for the presence of malignancy. There appeared to be no relationship between the level of preoperative serum Tennessee antigen and subsequent prognosis. Furthermore, in only nine of 31 patients did the serum Tennessee antigen level fall after removal of all macroscopic cancer. There also appeared to be no relationship between the level of serum TennaGen at three months after resection and subsequent prognosis. These findings are in contrast to estimations of serum carcinoembryonic antigen.

Antigens, Neoplasm↗

PubMed1982

Tennessee antigen: its value in the monitoring of patients with colorectal cancer.

Serial estimations of serum Tennessee antigen have been performed at regular three-month intervals on 35 patients with colorectal cancer who had undergone resection of all macroscopically obvious tumor but who were considered to be at high risk of developing subsequent metastases. The results were interpreted by a panel of surgeons in order to assess the clinical relevance of using serum Tennessee antigen for monitoring of patients. The serial estimation of serum Tennessee antigen was found to be very variable, difficult to interpret, and clinically unreliable as an accurate marker for the development of recurrent cancer in this group of patients. There are unacceptably high false-positive and false-negative diagnostic rates for serum Tennessee antigen estimations in comparison with serial estimations of carcinoembryonic antigen.

Antigens, Neoplasm↗

PubMed1981

Value of serial carcinoembryonic antigen determinations for early detection of recurrent cancer.

Carcinoembryonic antigen (CEA) has been monitored at intervals of approximately three months in patients who had undergone potentially curative surgery for breast cancer, head and neck cancer, lung cancer, and colorectal cancer, but who were considered to be at high risk of recurrence. Monitoring of CEA in patients' serum was of no value for the early detection of tumour recurrence in either breast or head and neck cancer patients. It was of value for the early detection of lung cancer recurrence, but these patients were always beyond the scope of cure. In colorectal cancer patients, two-thirds of recurrences were heralded by a rising CEA, but only one of 15 patients had disease confined to local tissues which could be totally excised, although a further three patients had liver metastases which were apparently localized to one lobe of the liver. For colorectal cancer patients, serial CEA estimations are an effective method for the early diagnosis of recurrence, although this seldom translates into improved patient benefit.

Breast Neoplasms↗

PubMed1981

Serum glycoproteins in diagnosis and monitoring of patients with large-bowel cancer.

The profile of serum glycoproteins is altered in malignancy with a relative increase in acute phase reactant proteins. A prospective study has been performed to investigate three sugar moieties (hexose, hexosamine and sialic acid) of these glycoproteins in the serum of large-bowel cancer patients as a possible guide to recurrence, and to compare these three variables with carcinoembryonic antigen (CEA). The three variables indicated the presence of colorectal cancer in over 65 per cent of 107 cancer-bearing subjects. Furthermore, the appearance of metastatic disease was associated with abnormalities in these variables in 10 of 11 patients, and appears more accurately reflected than with CEA. However, the three variables and CEA are cumulative in their value for predicting recurrent cancer. Monitoring of acute phase reactant proteins may therefore be of potential clinical benefit for monitoring of colorectal cancer patients at high risk of recurrence.

Carcinoembryonic Antigen↗

PubMed1979

Chemotherapy in the management of invasive bladder cancer. A review.

In this review of the management of invasive carcinoma of the bladder the results of primary and systemic therapies are evaluated in the light of the natural history of the disease. The clinical and pathological causes of treatment failure are assessed in an attempt to identify new approaches that may be used in the future management of patients with bladder cancer. To improve survival in this disease requires different approaches to both the control of local disease and the early control of metastatic disease.

Adult↗

PubMedDate not supplied

AIDS and prehospital personnel: knowledge and prevention of occupational exposure.

OBJECTIVES: Prehospital personnel, including law enforcement officers, paramedics, and fire-fighters, may be exposed to the human immunodeficiency virus (HIV) while working. This study of prehospital personnel sought to determine: 1) their knowledge of the acquired immune syndrome (AIDS) and HIV transmission; 2) the extent of AIDS training received; 3) self-assessment of risk for HIV infection; and 4) precautions adopted to reduce occupational risk of exposure to HIV. METHODS: A survey was administered to pre-hospital personnel in a large Southern California jurisdiction. The response rate was 41% (n = 1,756) in 10 city and county departments where respondents were employed. Law enforcement officers (44%), firefighters (44%), and paramedics (12%) comprised the sample. RESULTS: Respondents had accurate knowledge about AIDS, but incorrect perceptions about HIV transmission. A minority believed that HIV could be contracted from casual contact. Training relating to AIDS was not frequent. Preventive practices were infrequent in the work setting, with precautions used less than 50% of the time on eight of 10 measures. One-third of these prehospital personnel assessed their risk for HIV infection as medium to high, largely attributable to fear of occupational exposure. CONCLUSIONS: Improved educational programs regarding HIV/AIDS are needed for prehospital personnel to increase the use of preventive occupational practices in the field.

AIDS Serodiagnosis↗

PubMedDate not supplied

Growth hormone receptor and serum binding protein: purification, cloning and expression.

A putative growth hormone receptor from rabbit liver and the growth hormone binding protein from rabbit serum have the same amino-terminal amino-acid sequence, indicating that the binding protein corresponds to the extracellular hormone-binding domain of the liver receptor. The complete amino-acid sequences derived from complementary DNA clones encoding the putative human and rabbit growth hormone receptors are not similar to other known proteins, demonstrating a new class of transmembrane receptors.

Amino Acid Sequence↗