Expression of the hMSH6 mismatch-repair protein in colon cancer and HeLa cells

PRINCIPLES

10 to 15% of human colon cancers are associated with an inherited or somatic defect of the DNA Mismatch Repair (MMR) system, which has evolved to correct biosynthetic errors such as nucleotide mis-incorporations or misalignments arising during DNA replication in the S phase of the cell-cycle. Although expression of the MMR genes was expected to be cell-cycle dependent, we and others observed that the MMR proteins hMSH2 and hMLH1 are expressed constitutively in proliferating cells.

METHODS

In this study we extend our observations to another essential MMR protein, hMSH6. We used immunohistochemistry to evaluate the expression pattern of this protein in human colorectal mucosa and tumours, as well as in synchronised HeLa-S3 cells, in which we analysed its steady-state levels during the cell-cycle.

RESULTS

We show that the immunohistochemical pattern of expression of hMSH6 in normal colorectal crypts and in colon cancers differs significantly from that of the other MMR proteins, with a much lower percentage of replicating cells being hMSH6-positive. This implies that hMSH6 could be cell-cycle regulated. In order to test this hypothesis in a model system, we synchronised HeLa-S3 cells with mitotic shake-off and found that the hMSH6 protein was detectable throughout the cell-cycle, but that its steady-state level increased when cells progressed from G1 to S-phase.

DISCUSSION

The increase of hMSH6 steadystate level when cells enter S-phase was expected, since MMR acts during DNA replication. However, the overall low level of oscillations of hMSH6 during the cell-cycle in this cellular model apparently does not fit the immunohistochemical phenotype. We believe that this discrepancy is due to the fact that human cell lines proliferate at a much higher rate than normal and neoplastic colorectal cells in vivo.

Expression of the hMSH6 mismatch-repair protein in colon cancer and HeLa cells

PRINCIPLES

10 to 15% of human colon cancers are associated with an inherited or somatic defect of the DNA Mismatch Repair (MMR) system, which has evolved to correct biosynthetic errors such as nucleotide mis-incorporations or misalignments arising during DNA replication in the S phase of the cell-cycle. Although expression of the MMR genes was expected to be cell-cycle dependent, we and others observed that the MMR proteins hMSH2 and hMLH1 are expressed constitutively in proliferating cells.

METHODS

In this study we extend our observations to another essential MMR protein, hMSH6. We used immunohistochemistry to evaluate the expression pattern of this protein in human colorectal mucosa and tumours, as well as in synchronised HeLa-S3 cells, in which we analysed its steady-state levels during the cell-cycle.

RESULTS

We show that the immunohistochemical pattern of expression of hMSH6 in normal colorectal crypts and in colon cancers differs significantly from that of the other MMR proteins, with a much lower percentage of replicating cells being hMSH6-positive. This implies that hMSH6 could be cell-cycle regulated. In order to test this hypothesis in a model system, we synchronised HeLa-S3 cells with mitotic shake-off and found that the hMSH6 protein was detectable throughout the cell-cycle, but that its steady-state level increased when cells progressed from G1 to S-phase.

DISCUSSION

The increase of hMSH6 steadystate level when cells enter S-phase was expected, since MMR acts during DNA replication. However, the overall low level of oscillations of hMSH6 during the cell-cycle in this cellular model apparently does not fit the immunohistochemical phenotype. We believe that this discrepancy is due to the fact that human cell lines proliferate at a much higher rate than normal and neoplastic colorectal cells in vivo.

Skills of lay people in checking the carotid pulse

American Heart Association as well as European Resuscitation Council require the carotid pulse check to determine pulselessness in an unconscious victim and to decide whether or not cardiopulmonary resuscitation (CPR) should be initiated. Recent studies on the ability of health professionals to check the carotid pulse have called this diagnostic tool in question and led to discussions. To contribute to this discussion we performed a study to evaluate skills of lay people in checking the carotid pulse. A group of 449 volunteers (most had participated in a first aid course) were asked to check the carotid pulse in a young healthy, non-obese person by counting aloud the detected pulse rate. Time intervals until correct detection of the carotid pulse were registered. Overall the volunteers needed an average of 9.46 s, ranging from 1 to 70 s. Only 47.4% of the volunteers were able to detect a pulse within 5 s, and 73.7% within 10 s. A level of 95% volunteers detecting the pulse correctly was reached only after 35 s. Based on these findings we conclude that the intervals established for carotid pulse check may be too short and that perhaps the value of pulse check within in the scope of CPR needs to be reconsidered.

ACD versus standard CPR in a prehospital setting

BACKGROUND

Animal and human studies in cardiac arrest demonstrate significant improvements in systolic blood pressure, coronary perfusion pressure and total brain and myocardial blood flow with active compression-decompression (ACD) cardiopulmonary resuscitation (CPR). The results of recent studies in patients with out-of-hospital cardiac arrest and use of ACD-CPR are non-uniform and require supplementation.

METHODS

In a retrospective non-randomised design, 152 adult patients with prehospital cardiac arrest, not caused by trauma or hypothermia, were studied. Compressions were performed according to the recommendations of the American Heart Association. Three ACD devices were assigned to seven rescue units changing monthly. Study end-points were the rates of return of spontaneous circulation (ROSC), admission to hospital, survival at 24h, hospital discharge and neurologic outcome.

RESULTS

70 (46%) patients underwent standard (STD) CPR and 82 (54%) patients were treated with ACD-CPR. Both groups were comparable with regard to age, sex, witnessed cardiac arrests, bystander CPR, cause of arrest, time intervals, number of defibrillations, and total amount of epinephrine. No significant differences in outcome could be found: 20 patients (29%) who received STD-CPR, and 14 patients (17%) who underwent ACD-CPR survived to hospital discharge. Neither at other end-points nor in any subgroups could any significant differences be discovered. Patients regaining ROSC showed a significant difference in favour of STD-CPR for the end-points of hospital admission, 24-h survival and hospital discharge.

CONCLUSION

No significant differences in hospital discharge and neurological outcome were found between STD-CPR and ACD-CPR.

Early defibrillation by emergency physicians or emergency medical technicians? A controlled, prospective multi-centre study

In a controlled, prospective multi-centre study, defibrillation by emergency medical technicians (EMTs) was compared with the current standard of care in Germany--defibrillation by emergency physicians (EPs)-in order to answer the following questions: can EMTs in a two-tiered emergency medical services (EMS) system with physicians in the field defibrillate earlier than, and as safely as EPs? Does defibrillation by EMTs (study group) affect survival rate and long-term prognosis of patients in ventricular fibrillation (VF), as compared with the current national standards in resuscitation (basic cardiopulmonary resuscitation (CPR) by EMTs, and defibrillation by physicians: control group?

METHODS

Prior to the onset of the study, all EMTs completed retraining in basic life support (BLS). Randomly assessed EMTs were then trained to use semi-automatic defibrillators. With the help of on-line tape recordings, the complete resuscitation sequence was evaluated. Follow-up of the patients was carried out with the help of the Glasgow Coma Scale as well as Pittsburgh Cerebral and Overall Performance Categories.

RESULTS

A total of 159 patients with VF were included in the study. In 121 cases, collapse was witnessed. Of the patients receiving defibrillation by EMTs 25% were discharged from hospital alive, compared to 24% of the patients defibrillated by EPs. Of the study patients 67% were defibrillated within 12 min, while the percentage of control patients was 46%. Study patients were defibrillated earlier (P < 0.01), the return of spontaneous circulation (ROSC) was achieved earlier (P < 0.05), and the rate of patients requiring no adrenalin during resuscitation was higher in the study group (P < 0.05). The total amount of adrenalin administered in the study group was lower (P < 0.05). No statistically significant differences were found concerning the neurologic long-term prognosis.

CONCLUSIONS

In our study, EMT defibrillation was equally effective as defibrillation by EPs, but failed to improve survival rates or long-term outcome of patients in VF significantly, compared to EP defibrillation. Due to a reduction in the time intervals from collapse to defibrillation and to ROSC, as well as in adrenalin doses, by EMT-defibrillation, EMTs in Germany should defibrillate if they reach a patient prior to an EP, provided they have received continuous medical training and supervision.

[Initial defibrillation by emergency physicians or by first aid assistants? A prospective, comparative multicenter study in outpatients with ventricular fibrillation]

In a controlled prospective randomized study, defibrillation by emergency medical technicians (EMTs) was compared with the current standard of care in Germany (basic life support by EMTs and defibrillation by emergency physicians only) in order to answer the following questions: 1. Does EMT defibrillation improve the survival rate and long-term prognosis of patients in ventricular fibrillation as compared to the current German standards in resuscitation (basic life support by EMTs and defibrillation by emergency physicians)? 2. Are the prerequisites for the use of semiautomatic defibrillators fulfilled in the emergency medical systems (EMS) of the participating centers? METHODS. The study phase includes randomization of 121 adult patients with witnessed cardiac arrest and ventricular fibrillation (VF) as first ECG rhythm. Prior to the onset of the study, all EMTs of the participating EMS systems were retrained in basic life support (BLS) measures. In each center, randomly assessed EMT-Ds (EMTs trained in Defibrillation) were trained to use semiautomatic defibrillators. With the help of one-line tape recording, the time intervals during resuscitation and treatment steps were evaluated. Successfully resuscitated patients were followed up with the help of the Glasgow Coma Scale and the Pittsburgh Cerebral and Overall Performance Categories. RESULTS. From 1 February 1991 until 28 June 1992, 159 patients with VF were randomized. In 121 cases, collapse was witnessed. 25% (14/57) of the patients receiving defibrillation by EMT-Ds (study group = S) were discharged from the hospital alive. In the control group, 52 patients were defibrillated by emergency physicians, following BLS by EMTs [control group 1 = C1; discharged: 29% (15/52)]. Fifty patients received BLS and advanced cardiac life support (ACLS) by the emergency physicians crews [control group 2 = C2; discharged: 18% (9/20)]. In the study group, the median time interval from collapse of the patient until initiation of BLS measures was 7.7 min, 7 min in C1 and 8 min in C2. ACLS measures were initiated significantly earlier (P < 0.05) in the control groups, as compared to the study group [S: 13 min, C1: 11 min; C2: 10.3 min]. Sixty-seven percent (30/45) of the study patients and 46% (36/76) of the control patients were defibrillated within 12 min. Study patients were defibrillated earlier (P < 0.05) (S: 9.9 min; C1: 12.2 min; C2: 12.75 min); return of spontaneous circulation (ROSC) was achieved earlier (P < 0.05) in the study group [S: 14 min; C1: 19 min; C2: 18.2 min] and the number of patients in the study group requiring no epinephrine during resuscitation was higher (P < 0.01) than in the control groups [S: 35.3% (12/34); C1: 10% (4/40); C2: 10.5% (4/38)]. Furthermore, the total amount of epinephrine [mean (+/- standard error)] administered in the study group [S: 2.35 (+/- 0.49) mg; C1: 6.71 (+/- 0.98) mg; C2: 7.71 (+/- 1.31) mg] was significantly lower (P < 0.05). No significant differences in neurological long-term prognosis were found for the groups investigated. CONCLUSION. Neither the initial survival rate the number of patients discharged alive, nor the neurological long-term prognosis was significantly different for any of the groups investigated. Because of apparent differences in indirect prognostic parameters (time interval until ROSC, number of patients requiring no epinephrine) and because of the fact that the time interval to the first defibrillation was reduced by EMT defibrillation, EMT-Ds may perform defibrillation if: (a) they reach the patient before the emergency physician and (b) if they are trained intensively and supervised continuously. In order to increase the efficiency of defibrillation by EMT-Ds, far-reaching changes in our EMS are mandatory: (a) a reduction in the time interval from collapse until initiation of BCLS measures by intensifying layperson CPR training; (b) an increase in the number of emergency units equipped with semiautomatic defibril

In vitro effects of monoterpenes on chloroplast membranes

A chloroplast preparation was extracted from squash (Cucurbita pepo (L.) var. Senator). Enrichment of intact chloroplasts was achieved by continuous free-flow electrophoresis. The addition of monoterpenes, detergent and free fatty acids changed the elecrophoretic separation pattern characteristically. Monoterpene-dependent degradation of envelope membranes could be prevented by addition of α-tocopherol prior to monoterpene incubation.Photosynthetic electron transport of photosystem II was completely inhibited by β-pinene, Triton X-100 and linolenic acid. Inhibition could be modulated by addition of α-tocopherol or lecithin (phosphatidylcholine) either before or after inhibition by monoterpenes and detergent.Percentage reconstitution of photosynthetic electron transport inhibited by β-pinene depended on light conditions and incubation time.