Structure and Reactivity of Hexacoordinate Hemoglobins

The heme prosthetic group in hemoglobins is most often attached to the globin through coordination of either one or two histidine side chains. Those proteins with one histidine coordinating the heme iron are called “pentacoordinate” hemoglobins, a group represented by red blood cell hemoglobin and most other oxygen transporters. Those with two histidines are called “hexacoordinate hemoglobins”, which have broad representation among eukaryotes. Coordination of the second histidine in hexacoordinate Hbs is reversible, allowing for binding of exogenous ligands like oxygen, carbon monoxide, and nitric oxide. Research over the past several years has produced a fairly detailed picture of the structure and biochemistry of hexacoordinate hemoglobins from several species including neuroglobin and cytoglobin in animals, and the nonsymbiotic hemoglobins in plants. However, a clear understanding of the physiological functions of these proteins remains an elusive goal. The aim of this research was to understand physiological functions based on the molecular structure of plant hemoglobins. All plants contain hemoglobins that fall into distinct phylogenetic classes. The subset of plants that carry out symbiotic nitrogen fixation express hemoglobins that scavenge and transport oxygen to bacterial symbiotes within root nodules. These “symbiotic” oxygen transport hemoglobins are distinct in structure and function from the non-oxygen transport (“nonsymbiotic”) Hbs found in all plants. Hemoglobins found in two closely related plants present a paradox concerning hemoglobin structure and function. Parasponia andersonii is a nitrogen fixing plant that expresses a symbiotic hemoglobin (ParaHb) characteristic of oxygen transport hemoglobins in having a pentacoordinate ferrous heme iron, moderate oxygen affinity, and a relatively rapid oxygen dissociation rate constant. A close relative that does not fix nitrogen, Trema tomentosa, expresses hemoglobin (TremaHb) sharing 93% amino acid identity to ParaHb, but its phylogeny predicts a typical nonsymbiotic hemoglobin with a hexacoordinate heme iron, high oxygen affinity, and slow oxygen dissociation rate constant. We characterized heme coordination and oxygen binding in TremaHb and ParaHb, along with their crystal structures, to investigate whether or not two hemoglobins with such high sequence similarity are actually so different in functional behavior. Our results demonstrate distinct mechanisms for convergent evolution of oxygen transport in different phylogenetic classes of plant hemoglobins

Origin of cystic artery from hepatic artery proper and its surgical implications

Cystic artery is usually a branch of right hepatic artery given in the Calot’s triangle. Variations in the origin of cystic artery have been reported but there is paucity of literature regarding these in Indian subjects. The present case describes the origin of cystic artery from the hepatic artery proper, with an unusual course, which was detected during routine cadaveric dissection. The development of biliary vasculature is quite complex and it accounts for many variations. Knowledge of cystic artery variability facilitates intraoperative identification of vessels in both classical and laparoscopic surgery of the bile ducts. This emphasises the importance of a thorough knowledge of the cystic arterial variations that often occur and may be encountered during both laparoscopic and open cholecystectomy. Uncontrolled bleeding from the cystic artery and its branches is a serious problem that may increase the risk of intraoperative lesions to vital vascular and biliary structures during hepatobiliary surgery

Histological findings of testicular biopsy in North Indian population

Background: Infertility is defined as the inability to achieve pregnancy after one year of unprotected intercourse. To interpret these testicular causes, biopsy of testis and its classification becomes an important tool for diagnoses. Biopsy is mostly done in severe oligozoospermic or azoospermic patients. Biopsies are also important in recent times due to introduction of Assisted Reproductive Techniques (ART) because they determine the level of spermatogenesis. In the present study the testicular biopsy has been classified into seven categories. One of the classification is that of the highly homogenous mass, which is an addition to the studies done previously. The increase in connective tissue has been demonstrated by Masson’s trichrome stain not cited in the literature. This study will help relook into the way of categorising the testicular biopsy which will benefit those seeking treatment of male infertility.Methods: The study was carried out on 30 infertile patients who were either azoospermic (nil to <2 x106 sperms/ml) or severe oligozoospermic (<5 x106 sperms/ml). Testicular biopsy of these patients was taken after obtaining ethical clearance and written consent of the patients. The biopsy was processed, stained and assessed using haematoxylin and eosin and Masson’s trichrome. They were classified into different histological types. They were also categorised by modified Johnsen scoring.Results: The biopsies were classified histologically into obstructive azoospermia in 4 cases (13.33%). Hypospermatogenesis in 5 cases (16.66%), maturation arrest in 3 cases (10%), sertoli cell only syndrome in 3 cases (10%), seminiferous tubule hyalinization in 7 cases (23.33%), mixed patterns in 6 cases (20%) and highly cellular homogenous tissue in 2 cases (6.66%). The last condition has not been classified in the literature cited.Conclusions: By the present study we can determine the level of spermatogenesis and by studying the nature of different germ cells we can use it for ART. Consideration of the biopsy being taken from a particular part of the testis must be kept in mind, and there might be the possibility of spermatogenesis occurring in some other quadrant. The patient needs to be explained this

Structure and Reactivity of Hexacoordinate Hemoglobins

The heme prosthetic group in hemoglobins is most often attached to the globin through coordination of either one or two histidine side chains. Those proteins with one histidine coordinating the heme iron are called “pentacoordinate” hemoglobins, a group represented by red blood cell hemoglobin and most other oxygen transporters. Those with two histidines are called “hexacoordinate hemoglobins”, which have broad representation among eukaryotes. Coordination of the second histidine in hexacoordinate Hbs is reversible, allowing for binding of exogenous ligands like oxygen, carbon monoxide, and nitric oxide. Research over the past several years has produced a fairly detailed picture of the structure and biochemistry of hexacoordinate hemoglobins from several species including neuroglobin and cytoglobin in animals, and the nonsymbiotic hemoglobins in plants. However, a clear understanding of the physiological functions of these proteins remains an elusive goal. The aim of this research was to understand physiological functions based on the molecular structure of plant hemoglobins. All plants contain hemoglobins that fall into distinct phylogenetic classes. The subset of plants that carry out symbiotic nitrogen fixation express hemoglobins that scavenge and transport oxygen to bacterial symbiotes within root nodules. These “symbiotic” oxygen transport hemoglobins are distinct in structure and function from the non-oxygen transport (“nonsymbiotic”) Hbs found in all plants. Hemoglobins found in two closely related plants present a paradox concerning hemoglobin structure and function. Parasponia andersonii is a nitrogen fixing plant that expresses a symbiotic hemoglobin (ParaHb) characteristic of oxygen transport hemoglobins in having a pentacoordinate ferrous heme iron, moderate oxygen affinity, and a relatively rapid oxygen dissociation rate constant. A close relative that does not fix nitrogen, Trema tomentosa, expresses hemoglobin (TremaHb) sharing 93% amino acid identity to ParaHb, but its phylogeny predicts a typical nonsymbiotic hemoglobin with a hexacoordinate heme iron, high oxygen affinity, and slow oxygen dissociation rate constant. We characterized heme coordination and oxygen binding in TremaHb and ParaHb, along with their crystal structures, to investigate whether or not two hemoglobins with such high sequence similarity are actually so different in functional behavior. Our results demonstrate distinct mechanisms for convergent evolution of oxygen transport in different phylogenetic classes of plant hemoglobins.</p

Structure and Reactivity of Hexacoordinate Hemoglobins

The heme prosthetic group in hemoglobins is most often attached to the globin through coordination of either one or two histidine side chains. Those proteins with one histidine coordinating the heme iron are called “pentacoordinate” hemoglobins, a group represented by red blood cell hemoglobin and most other oxygen transporters. Those with two histidines are called “hexacoordinate hemoglobins”, which have broad representation among eukaryotes. Coordination of the second histidine in hexacoordinate Hbs is reversible, allowing for binding of exogenous ligands like oxygen, carbon monoxide, and nitric oxide. Research over the past several years has produced a fairly detailed picture of the structure and biochemistry of hexacoordinate hemoglobins from several species including neuroglobin and cytoglobin in animals, and the nonsymbiotic hemoglobins in plants. However, a clear understanding of the physiological functions of these proteins remains an elusive goal

Clinical importance of duodenal recesses with special reference to internal hernias

Introduction: The detailed knowledge of the peritoneal recesses has great significance with respect to internal hernias. The recesses are usually related to rotation and adhesion of abdominal viscera to the posterior abdominal wall and/or the presence of retroperitoneal vessels which raises the serosal fold. The duodenal recesses are usually related to the 3rd and 4th parts of the duodenum. Internal hernias with respect to these recesses are difficult to diagnose clinically and usually noticed at the time of laparotomy. So, the knowledge of these recesses can be valuable to abdominal surgeons. Material and methods : The present study was conducted in 100 cases including 10 cadavers, 45 post mortem cases and 45 cases undergoing laparotomy. Results : We found superior and inferior duodenal recesses in 28% and 52% respectively, paraduodenal in 12%, mesentericoparietal in 3%, retroduodenal in 2% and duodenojejunal in 18% of cases. Two abnormal duodenojejunal recesses were found, one on the right (instead of the left) of the abdominal aorta, and in the other the opening was directed upwards instead of downwards. The incidence of internal hernias was 3%. Conclusions : Thus it was observed that there is low incidence of superior and inferior duodenal recesses, and high incidence of paraduodenal recess. The abnormal recesses might be due to malrotation of the gut. In laparotomy cases, the internal hernia was noticed when the abdomen was opened for intestinal obstruction. The incidence of internal hernia was found to be high